White House National Security Adviser Jake Sullivan said there was "reason to believe" a US hostage would be released from captivity in Gaza on Sunday.
"We have reason to believe that one of those Americans will be released today," Sullivan told NBC's "Meet the Press".
Sullivan declined to give the identity of the hostage who might be released. When asked whether it was a four-year-old girl whose parents were killed, he said: "We have a sense of who it is but I am just not in a position to confirm it."
Israel and Hamas have agreed to swap 50 hostages held by the Palestinian terrorist group for 150 prisoners in Israeli jails over a four-day truce period.
So far, Hamas has released 26 Israelis and four Thai nationals it had held as hostages, while Israel has freed 78 Palestinians.
Egypt, which is helping to mediate the deal, says it has received lists of 13 Israelis and 39 Palestinians scheduled for a third release on Sunday.
The Israel-Hamas war
It is the first halt in the conflict since Hamas fighters rampaged through southern Israel on Oct. 7, killing 1,200 people and taking about 240 hostages.
In response to that attack, Israel vowed to destroy the Hamas terrorists who run Gaza, bombarding the enclave and mounting a ground offensive in the north.
Hamas health authorities say some 14,800 people, roughly 40% of them children.
This is a developing story.