President Joe Biden praised the release of hostages Sunday from the Gaza Strip and said he hopes the four-day cease-fire will be extended.

"Look, you know the deal calls for every 10 hostages released, we extend another day. So, I'm hopeful this is not the end, it's going to continue. But we don't know. But I get a sense that all the players in the region, even the neighbors who haven't been directly involved [up] to now, are looking for a way to end this so the hostages are all released and Hamas is completely, how can I say it, no longer in control of any portion of Gaza," Biden said at a press conference.

"I'd like to see the pause go on as long as prisoners keep coming out," he added.

Biden said there are probably other militant groups that have hostages in the Gaza Strip, and that the condition of the other Americans being held in Gaza is unclear.

The president's remarks come as 4-year-old Abigail Idan was among the hostages released Sunday.

Idan's parents were killed in front of her during the October attack in southern Israel, U.S. officials have said.

"She's been through a terrible trauma," Biden said. "What she endured is unthinkable."

Israel and Hamas are currently on the third day of a four-day pause in fighting during which Israel plans to release 150 Palestinians and Hamas will release 50 of the over 200 people it is thought to have taken hostage on Oct. 7.

Abigail Idan, a 4-year-old Israeli American, was among the 17 hostages released to the Red Cross on Sunday, according to the Israeli prime minister's office.

Abigail, who turned 4 on Friday, was taken hostage on Oct. 7 after her parents were killed by Hamas terrorists, according to Israeli officials.

Another Israeli American, Aviva Adrian Siegel, 62, was also freed on Sunday, the Israeli prime minister's office said.

"We were overjoyed. Couldn't believe it," Siegel's brother-in-law, David Siegel told ABC News, adding that the family had been doubtful she would be released.

The Israel Defense Forces said 13 hostages were returned to Israel accompanied by IDF forces and are now in Israeli territory, with 12 being escorted to the Hatzerim base and another having gone to a hospital. Four more hostages are on their way to the Rafah crossing, the IDF said.

Other Israeli hostages released on Sunday were identified by the Israeli prime minister's office as:

Fourteen more Israeli hostages and three foreign nationals were released to the Red Cross on Sunday by Hamas, according to an Israel Defense Forces spokesperson.

At least one of the foreign nationals is Russian, according to a statement by the Al-Qassam Brigades, Hamas' military wing.

"In response to the efforts of Russian President Vladimir Putin and in appreciation of the Russian position in support of the Palestinian cause, the Islamic Resistance Movement Hamas has released a detainee of a Russian nationality," the statement said.

No Americans were among the hostages released.

"As part of the humanitarian truce and within the third phase of the exchange, we handed over to the Red Cross 13 Israeli detainees, 3 Thai detainees, and one Russian detainee," the Al-Qassam Brigades said in another statement.

-ABC News' Ayat Al-Tawy and Becky Perlow

One American hostage could be released from Gaza on Sunday as part of a prisoner exchange between Israel and Hamas, White House national security adviser Jake Sullivan told ABC "This Week."

"This first set of hostages, 50 hostages over four days, is women and children -- and three Americans [are] in that category, two women and one child," Sullivan told "This Week" co-anchor Jonathan Karl. "We have reason to believe one of those Americans will be released today."

Still, Sullivan cautioned, "Until we actually see her safe and sound ... we cannot have 100% certainty that it will happen. So we're going to watch this hour by hour and hopefully have a moment of joy where one of the Americans is safely out and ultimately reunited with her family. That's what we are waiting for as we speak."

-ABC News' Tal Alexrod

The first group of Israeli hostages have been released by Hamas in the Gaza Strip and handed over to the International Committee of the Red Cross, two sources briefed on the matter told ABC News.

The sources said the Red Cross has the hostages and that the "operation" to get them home has begun.

It was expected that 13 Israeli hostages would be freed by Hamas near Gaza's border with Egypt on Friday in a prisoner exchange deal. But it was unclear exactly how many were handed over to the Red Cross.

-ABC News' Matt Gutman and Morgan Winsor