Hamas did change some of the terms of the ceasefire negotiations, making reaching a deal more difficult, National Security Communications adviser John Kirby told reporters on Monday, though he said "it's still worth an effort to get back into it."
Kirby described Hamas as the main obstacle to reaching the deal.
Hamas's new demands call into question their readiness to do a deal at all, Press Secretary Karine Jean-Pierre added.
"Even though we're hearing that, we want to talk about the next steps," she said.
The murder of the six hostages last weekend made the urgency for a deal even more clear, Jean-Pierre said.
When asked if the White House was prepared to apply pressure on Israel, like withholding weapons, Kirby said he "couldn't think of anything we haven't put more pressure on ourselves than to try and get this deal."
US refrains from interfering with UK-Israel relations
"We know how urgent this is, and we're working night and day to try to get a deal in place," Kirby said.
Biden will not try to convince Prime Minister Keir Starmer to reverse his government's decision to suspend some arms to Israel during their meeting at the White House on Friday as the "British government has made their determination, Kirby said.
The leader's meetings will be about "how we move together as principal allies."
Kirby said Biden has not yet spoken to the family of Aysenur Eygi, though Israel reached out to the White House and "made sure we knew they were promptly investigating."
Israel should be able to present its findings in the coming days, according to Kirby.