Ukrainian President Volodymyr Zelenskyy thanked U.S. President Joe Biden for additional sanctions taken against Russia on Tuesday, saying they will "significantly weaken the occupiers."

The new measures include a ban on imports of oil, petroleum products, gas and coal from Russia. U.S. citizens are also now prohibited from investing in Russia's fuel and energy sector.

"A ban on oil imports to the United States will weaken the terrorist state economically, politically and ideologically, because it is about freedom -- about the future, about where the world will move," Zelenskyy said, adding that he is "personally grateful" to Biden.

Zelenskyy also expressed gratitude to U.K. Prime Minister Boris Johnson for instating a similar ban, describing Johnson as "a man of his word, a sincere friend of Ukraine."

-ABC News' Christine Theodorou

Even with a series of harsh measures already taken on Russia, including a ban on Russian imports, the sanctioning of Russia’s central bank and the enactment of export controls, the U.S. could enact even tighter sanctions, several experts told ABC News.

The U.S. could push other countries to make commitments to decrease their reliance on Russian energy -- which it and the U.K. are already beginning to do -- and to increase their own production of oil and gas to lower the high energy prices Americans and Europeans are starting to face — and it could also get Saudi Arabia, Venezuela and others to increase their exports.

Other current sanctions the U.S. could tighten include imposing "full-blocking" sanctions, the harshest possible financial sanctions, on Sberbank, Russia’s largest bank. The U.S. has already done this for several other banks but has only put limited restrictions on Sberbank in order to limit the impact on the ordinary Russians who use the bank.

The U.S. could also put additional secondary sanctions on banks, put more restrictions on Russian goods, keep pursuing oligarchs and other Russian elites and sanction other Russian sectors such as minerals, chemicals, and coal.

The sanctions the West has already imposed have devastated the Russian economy at a rapid clip. They will continue to compound and inflict more pain on the Russian economy as they continue to play out, the experts said.

-ABC News' Ben Gittleson

The Coca-Cola Company and PepsiCo have suspended business in Russia, the companies announced Tuesday.

"Our hearts are with the people who are enduring unconscionable effects from these tragic events in Ukraine," the release states. "We will continue to monitor and assess the situation as circumstances evolve."

Pepsi, which has ben operating in Russia for more than 60 years, "must stay true to the humanitarian aspect of our business," CEO Ramon Laguarta wrote in a letter to PepsiCo associates.

"Our first priority continues to be the safety and security of our fellow Ukrainian associates," Laguarta said. "We suspended operations in Ukraine to enable our associates to seek safety for themselves and their families, and our dedicated crisis teams in the sector and region continue to closely monitor developments in real time."

Pepsi will also continue to provide aid to assist Ukrainians refugees in neighboring countries, including donating milk and refrigerators to relief organizations, and we’re ramping up production of foods and beverages in neighboring countries to meet the increased need, Laguarta said.

-ABC News' Will Gretsky

The White House is not engaging in speculation about how high crude oil prices will spike but said Americans will not be asked to stay home to cut down on gas usage.

"We’re neither going to make a prediction, or -- nor are we going to tell Americans to stay home," White House press secretary Jen Psaki told reporters on Tuesday.

Some House Democrats, such as Rep. Hakeem Jeffries, D-N.Y., on Tuesday morning, have suggested that asking the federal government and private business to encourage working from home would ease the demand for fuel and help keep prices stable.

But Psaki dismissed the suggestion of ramping up work from home, as the administration has been working to move into the "endemic" phase of COVID-19, returning to more normalcy.

Upon arriving in Texas on Tuesday afternoon, U.S. President Joe Biden told reporters that there's little he can do about the soaring gas prices, blaming Russia for sparking the crisis.

"They're gonna go up," Biden said about gas prices after arriving in Fort Worth. "Can't do much right now. Russia's responsible."

-ABC News’ Sarah Kolinovsky

The Russian forces charging toward Kyiv haven't made progress in the last day as they face Ukrainian resistance and low food and gas supply, a senior U.S. defense official told reporters Tuesday.

However, it could be a deliberate pause, the official said. "Part of the stall could be ... as a result of their own self-determined sort of pause in operations -- that they are possibly regrouping, rethinking, reevaluating," the official said.

The U.S. believes Russian forces "have committed now more than 80% of what was their pre-staged combat power," the official added.

The official said some Russian soldiers weren't told they were going into combat. The official said "not all of them were apparently fully trained and prepared."

The strong Ukrainian resistance has also hurt morale, according to the official.

Russia has now launched more than 400 missiles on Ukraine, the official said. The U.S. believes Russia has launchers that could be used for thermobaric weapons, but cannot confirm their use, the official said.

Russian forces are making the most progress in the south. Russians are attacking Kherson in south Ukraine, which "appears very much to be contested city at this point," the official said.

Russians are also approaching Mariupol in southeastern Ukraine, and while they haven't yet entered the city, "they are close enough now that they could attack Mariupol with long range fires," the official said.

Two towns on the path to Mariupol are believed to be occupied by the Russians, according to the official.

The U.S. believes the Russians hope to move north out of Mariupol up to the heavily-contested city of Kharkiv. The official said they believe Russian forces are trying to encircle Kharkiv.

The U.S. official noted that they've seen "certain risk-averse behavior by the Russian military" over the last week.

"Take the amphibious assault, for instance. They put those troops ashore a good 70 kilometers away from Mariupol because they knew Mariupol was going to be defended and they could put them ashore in an uncontested environment. And they still haven't reached Mariupol," the official said.

"They are not necessarily willing to take high risks with their own aircraft and their own pilots," the official said.

"And of course we're seeing that on the ground -- the fairly slow and steady progress that they have made, and you guys are seeing it for yourselves on the ground where ... units are surrendering, sometimes without a fight."

-ABC News' Matt Seyler