Evan Gershkovich, Paul Whelan greeted by President Biden, VP Harris after landing on US soil

Former U.S. Marine Paul Whelan, Wall Street Journal reporter Evan Gershkovich and Alsu Kurmasheva, a Russian-American journalist, are back on U.S. soil.

As they stepped off the plane, President Joe Biden and Vice President Kamala Harris greeted the three at Joint Base Andrews outside Washington.

The Americans were part of an extraordinary 24-prisoner exchange involving Russia, the United States and several other countries, the largest of its kind since the Cold War and one in which President Biden was directly involved, the White House said earlier Thursday.

The swap allowed wrongfully detained Americans Gershkovich and Whelan to return home from Russia.

Addressing the press after greeting the Americans, Biden gave special recognition to Germany and Slovenia.

"The toughest call on this one was for other countries because I asked them to do things that were against their self-interest, especially Germany and Slovenia," Biden said.

When asked if exchanges like these make it more likely for Americans to be taken abroad, Biden said, "That's been the case for all history. My job is to make sure, No. 1, they don't get them, and if they do, we get them back."

Reporters also asked Biden if he had a message for Russian President Vladimir Putin.

"Stop," Biden replied.

After their arrival at JBA, the returning Americans and their families were set to be offered a flight to Lackland Air Force Base in San Antonio, Texas, to receive post-isolation support at San Antonio Brooke Army Medical Center, according to a senior administration official.

Shortly before noon Thursday, Gershkovich and Whelan had been freed and were on their way back to the U.S., Secretary of State Antony Blinken said.

The multipart deal is the product of months of detailed, painstaking negotiations, national security adviser Jake Sullivan said.

"Some of these women and men have been unjustly held for years. All have endured unimaginable suffering and uncertainty. Today, their agony is over," Biden said in a statement.

"This is a very good afternoon," Biden said not long after in remarks at the White House, surrounded by family members of those freed. "Moments ago, the families and I were able to speak to them on the telephone from the Oval Office. They're out of Russia."

Asked by a reporter what he told them, Biden responded, smiling, "I said, 'Welcome, almost home.'"

He said the deal was a "feat of diplomacy and friendship."

"This deal would not have been made possible without our allies. Germany, Poland, Slovenia, Norway, and Turkey, they all stepped up and they stood with us. They stood with us, and they made bold and brave decisions, released prisoners being held in their countries who were justifiably being held and provided logistical support to get the Americans home. So, for anyone who questions whether allies matter, they do. They matter," he said.

Planes believed to be carrying the freed prisoners were seen on arrival at Turkey's Ankara Airport earlier Thursday, the AP reported.

The exchange also freed Alsu Kurmasheva, a Russian-American journalist, and Vladimir Kara-Muza, a legal permanent resident of the U.S.

"The president is gathering the families of Paul Whelan, Evan Gershkovich, Alsu Kurmasheva and Vladimir Kara-Murza at the White House to share with them the news that an exchange is underway to secure the release of their loved ones from Russia," Sullivan told reporters on Thursday morning.

According to a senior administration official, Biden had been monitoring the situation "in near real time" through updates from his national security team, and was set to stay plugged in throughout of the day.

Release 'uniquely challenging'

Sullivan said securing the release of the Americans was "uniquely challenging" due to the strained relationship between the countries and the war in Ukraine.

Another hurdle, he said, was Russia's unwillingness to agree to a swap that did not include Vadim Krasikov, a Russian operative and hitman who was serving a life sentence in Germany for gunning down an opponent to the Kremlin on the streets of Berlin.

"That required extensive diplomatic engagement with our German counterparts, starting at the top with the president himself, who worked this issue directly with Chancellor Schultz. We are deeply grateful to Germany for their partnership," Sullivan said.

Gershkovich, 32, was arrested by Russian authorities in March 2023 for espionage, a charge he and U.S. officials flatly deny, with President Biden saying Gershkovich was targeted for being a journalist and an American.

After an unusually hasty trial that played out behind closed doors, Gershkovich was found guilty and sentenced to 16 years in a high-security penal colony.

Whelan, who holds U.S., British, Irish and Canadian citizenship, was arrested in December 2018 while traveling on an American passport in Russia and also accused of espionage.

Both the Biden and Trump administrations denied the allegation against Whelan. He was convicted on the charges in June 2020 and sentenced to 16 years in prison, ultimately serving five.

Kurmasheva, a dual citizen of the U.S. and Russia, was arrested by Russian authorities in 2023 for failing to register as a foreign agent. Kara-Muza was serving a 25-year sentence for criticism of the war in Ukraine.

As part of the exchange, Russia had also agreed to release a dozen German nationals who were being held as political prisoners.

Biden's role and US-Russia relations

A senior administration official said even on the day he announced he was no longer seeking reelection, President Biden was on the phone working to secure this deal.

"The hour before he released that statement – literally an hour before he released that statement – he was on the phone with his Slovenian counterpart urging them to make the final arrangements and get this deal over the finish line," the official said. "This exchange is not by accident. It really is the result of a heck of a lot of leadership by President Biden and by the strength of relationships," the senior administration official said.

A senior administration official says despite this significant agreement, there should be no expectation of improved U.S.-Russia relations going forward.

This official said the administration has shown it can hold Russia accountable for its aggression on the world stage while "compartmentalizing out" the work on securing the release of Americans that are wrongfully detained.

"I would be cautious and would counsel anyone to be cautious in surmising from this that it's some sort of break through in the relationship and it portends some detente with Russia or an easing of the tensions in our relationship."

This official said Russia's ongoing war against Ukraine, pressure on NATO allies and across Europe, and the "burgeoning defense relationship" Putin is forming with China, North Korea and Iran are "of significant concern," the official said.

"We will not see a policy change by President Biden and the administration when it comes to standing up to Putin's aggression," the official said.

Prisoners handed over by US

The three prisoners handed over from the U.S. are Roman Seleznev, Vladislav Klyushin and Vadim Konoshchenock.

The son of a Russian lawmaker, Seleznev was found guilty by a U.S. federal court in Washington State for running a cyber scheme targeting thousands of U.S. businesses, resulting in $169 million in losses. He was sentenced to 27 years in prison in 2017.

That same year, Seleznev pleaded guilty to participating in a racketeering scheme in Nevada and conspiracy to commit bank fraud in Georgia, receiving a 14-year jail term for each to run concurrently with the Washington sentence.

Klyushin, a Russian businessman linked to the Kremlin, was sentenced to nine years in prison in September 2023 after he was convicted of playing a key role in a stock market cheating scheme that relied on insider information obtained by hacking U.S. computer systems.

Konoshchenko was accused of smuggling American-made military equipment into Russia and laundering money for Moscow. He was awaiting trial and facing a maximum sentence of 30 years behind bars.

Apart from Krasikov, prisoners returning to Russia from other countries include two from Slovenia, one from Norway, and one from Poland.

Despite the groundbreaking nature of the deal, White House officials cautioned against seeing the agreement as a watershed moment for U.S.-Russia relations at large.

"We will not see a policy change by President Biden and the administration when it comes to standing up to Putin's aggression," one official said.

The deal comes as a surprise to Kremlin observers and some U.S. officials, who believed Vladimir Putin would be reticent to strike a deal that could be perceived as a win for the Biden administration.

The State Department revealed in December that the U.S. had put forward a "substantial proposal" to free Gershkovich and Whelan but said Russia had rejected it—although administration officials said negotiations between the countries pressed forward.

Former President Donald Trump, the Republican candidate for the White House, previously promised that he would free Gershkovich "as soon as I win the election."

Gershkovich and Whelan were the only two Americans imprisoned in Russia considered by the U.S. government to be wrongfully detained, but at least ten other U.S. citizens are jailed in the country under dubious circumstances, according to officials familiar with the matter.

One official said that the U.S. regretted it could not include Marc Fogel, an American school teacher arrested in Russia for trying to carry a small amount of medical marijuana into the country, as part of the swap.

In recent years, the U.S. and Russia have completed two straightforward one-for-one prisoner exchanges to free wrongfully detained Americans.

The countries swapped U.S. Marine Corps veteran Trevor Reed for Russian pilot Konstantin Yaroshenko, who was serving out a sentence for drug smuggling, in April 2022.

In December of the same year, Russia freed Brittney Griner, a WNBA basketball player, in exchange for the release of Viktor Bout, an arms dealer known as the "merchant of death."

The Wall Street Journal, in a statement, said, "We are overwhelmed with relief and elated for Evan and his family, as well as for the others who were released."

It added, "Specifically, we would like to thank the U.S. government and numerous governments around the world, with particular gratitude to Germany; global news media organizations standing in solidarity with Evan; Evan's vast international network of friends; and our colleagues at The Wall Street Journal, Dow Jones and News Corp who supported Evan from the first hour of his captivity."

On Thursday afternoon, Harris, the now presumptive Democratic Party nominee, as she left Houston, made a statement to cameras, notably mentioning her role in the prisoner release.

"Over many years, President Biden and I, and our team have engaged in complex diplomatic negotiations to bring these wrongfully detained Americans home," Harris said. "We never stopped fighting for their release, and today, in spite of all of their suffering, it gives me great comfort to know that their horrible ordeal is finally over."

ABC News' Fritz Farrow contributed to this report.