The White House expressed cautious confidence Sunday that an American citizen is among those set to be freed by Hamas in the latest hostage release in Gaza. 

The Islamist Palestinian group which launched a deadly attack on Israel on 7 October, triggering a brutal war, is holding 10 Americans hostage, including two women and one young girl, National Security Advisor Jake Sullivan said. 

"We have reason to believe that one of those Americans will be released today. But until we see her out safely from Gaza… ultimately in the hands of her family, then we won't be certain," Sullivan told NBC News show "Meet the Press," as he made a round of morning talk shows.

Sullivan declined to confirm whether the US citizen set for release is Abigail Mor Idan, whose parents were murdered by Hamas militants.

"We are hopeful that Abigail will be released. We think it's long past time that this little girl, who just… celebrated her fourth birthday, is back home" with relatives, he said. 

The latest negotiations over hostages were "unfolding as we speak," Sullivan said, as Hamas militants were set to release a third group of Israeli hostages in exchange for Palestinian prisoners amid a delicate truce.

"But we proceed with caution because we're dealing with a terrorist group."

About 215 hostages are believed to be still held by Hamas. In many cases, it is unknown whether they are alive or dead.

On the ABC News show "This Week," Sullivan said that while there is expectation Abigail is alive, "we have not gotten proof of life on any" American captives.

In exchange for the release of Gaza hostages, Israel has freed dozens of Palestinians from jail, leading to joyful scenes among Palestinians.

Asked whether that is helping Hamas's standing, Sullivan told ABC: "I can't deny that Hamas gained some benefits from this deal."

But "these are difficult decisions that any Israeli prime minister has to make," he said of the swaps.

US President Joe Biden is under mounting pressure to secure the release of Americans held in Gaza.

He has been personally engaged in the negotiation process, but his chief rival in the 2024 presidential race, Donald Trump, blamed poor American leadership for the lack of US citizen releases.

"There is only one reason for that, NO RESPECT FOR OUR COUNTRY OR OUR LEADERSHIP," Trump posted Saturday on Truth Social.