US President Joe Biden on Monday said Israeli Prime Minister Benjamin Netanyahu was not doing enough to secure a deal for the release of hostages taken by Palestinian group Hamas and a ceasefire.

Asked by reporters at the White House, where Biden was arriving for a meeting with US negotiators, if he thought the Israeli leader was doing enough on the issue, the president responded: "No."

Biden's meeting with the negotiators on the hostage-release deal comes after the deaths on Saturday of six captives in Gaza, including an American citizen.

"President Biden expressed his devastation and outrage at the murder, and reaffirmed the importance of holding Hamas's leaders accountable," a White House statement said after the meeting.

Biden and Vice President Kamala Harris, who is running to succeed him in November's US presidential election, were briefed by negotiators "on the status of the bridging proposal outlined by the United States, Qatar, and Egypt," the statement said.

Ahead of the meeting, Biden had said negotiators were "very close" to a final proposal to be presented to Israel and Hamas.

The White House said the Situation Room briefing had been attended by Secretary of State Antony Blinken, CIA Director William Burns, National Security Advisor Jake Sullivan, and other senior US officials.

The United States, along with fellow mediators Egypt and Qatar, has spent months claiming to be pushing for a hostage-prisoner exchange and ceasefire in the war in Gaza.

More than 40,786 Palestinians have been killed in Israel's military campaign in the Gaza Strip since the war began, according to the health ministry in Gaza.

Most of the dead are women and children, according to the UN's human rights office. (AFP)