Captives are expected to be released each day until Monday during pause in fighting.
“I think the chances are real,” he told reporters on Friday, while also refusing to speculate on how long the war that started on October 7 after a surprise Hamas attack inside Israel could last.
“My expectation and hope is that as we move forward, the rest of the Arab world and the region is also putting pressure on all sides to slow this down, to bring this to an end as quickly as we can,” Biden said, while reiterating his support for Israel.
He stressed that “eliminating” Hamas remains a “legitimate” mission for Israel.
He only said he has “encouraged” Israeli Prime Minister Benjamin Netanyahu to try to limit civilian casualties.
About 15,000 Palestinians, most of them women and children, have been killed so far in Israeli bombardments following the Hamas attack that killed 1,200 people in Israel.
Under the terms of the truce, which came into effect early on Friday, 50 women and children held in Gaza are to be released over four days, in exchange for 150 Palestinian women and children who are among thousands imprisoned in Israeli jails.
On Friday, 39 Palestinians were released in the occupied West Bank in exchange for Hamas releasing 24 captives, including 13 Israelis. More are expected to be released on Saturday afternoon.
After the release of the first Hamas-held captives, Biden said: “It’s only a start, but so far it’s gone well.”
Both Israel and Hamas have promised that they will continue to fight, but Israel has signalled it is open to extending the truce if more captives are released at a rate of 10 per day – something Biden said he hoped would come to pass.
Hamas has said the non-civilian Israelis it is holding will only be exchanged for the thousands of Palestinians who are languishing in Israeli prisons in harsh conditions, many of them held without charge.
About 200 trucks with humanitarian aid also made their way into the besieged enclave as part of the truce on Friday, with the first deliveries into northern Gaza since the start of the war arriving on Saturday.
But the level of destruction remains high both in the north and in the south of the Gaza Strip, and the United Nations confirmed on Friday that Israel significantly ramped up its attacks in Gaza before the truce came into effect.