Israeli Prime Minister Benjamin Netanyahu will deliver an address before the two houses of the U.S. Congress, his office confirmed Monday.

A date has not been set yet, his office said.

Plans for Netanyahu's address come after Congressional big four leaders invited Netanyahu in a joint letter sent Friday.

-ABC News' Jonathan Karl, Benjamin Siegel, Allison Pecorin and Bruno Nota

Israeli forces confirmed the deaths of four more hostages: Haim Peri, Yoram Metzger, Amiram Cooper and Nadav Popplewell.

IDF spokesman Daniel Hagari said the four hostages were "killed together" a "few months ago" while "IDF forces were operating" in Khan Younis in southern Gaza. Hagari said Israeli forces are "examining the circumstances" of their deaths.

Cooper, 85, was an economist and a poet, and a father of four and grandfather of 11, according to Kibbutz Nir Oz. His wife, Nurit Cooper, was also kidnapped and later released, the kibbutz said.

Metzger, 80, was a father of three and grandfather of seven. His wife, Tamar Metzger, was also abducted to Gaza and later released, the kibbutz said.

Popplewell, 51, was kidnapped with his mother, who has been released, the Hostages Families Forum said.

Peri, 80, was abducted while protecting his wife, the Hostages Families Forum said. He leaves behind his wife, five children and 13 grandchildren.

Peri's family said he "heroically survived in the Hamas tunnels, under inhumane conditions, for around 4 months," and he "survived with the hope and faith that the state of Israel will fulfill its moral duty to bring him home."

"The government of Israel and its Prime Minister have no right to leave the hostages in captivity, dismantling Israel’s foundational principle of mutual responsibility," Peri's family said. "We call upon the government of Israel to strive for an immediate deal, save those still alive, and bring those who are not, to a proper burial."

"The heartbreak that comes with this painful news should shake every citizen in the State of Israel and lead every leader to profound soul-searching," the Hostages Families Forum said in a statement Monday. "The Israeli government must send out a negotiating delegation this evening and return all 124 hostages, both living and murdered. ... We reiterate our demand to the Israeli government: approve the Netanyahu deal immediately!"

President Joe Biden told the emir of Qatar on Monday that Israel is ready to "move forward with the terms" of the hostage and cease-fire deal, according to the White House readout of the call.

Biden said that "Hamas is now the only obstacle to a complete ceasefire," and the president "urged [Qatar's Emir Sheikh Tamim bin Hamad Al Thani] to use all appropriate measures to secure Hamas’ acceptance of the deal," the White House said.

State Department spokesperson Matthew Miller said the current cease-fire proposal is "nearly identical to what Hamas said it would accept just a few weeks ago," and said the U.S. and other mediators had not yet received an official response to the proposal from the militant group.

"The world should know, the Palestinian people should know, that the only thing standing in the way of an immediate cease-fire today is Hamas," Miller declared.

Miller said there were some gaps between the proposal Hamas said it would agree to in the past, but added that the U.S., Qatar and Egypt all felt that they could be easily reconciled.

-ABC News’ Shannon Crawford

A weapon used in a strike on a UNRWA school sheltering displaced people on June 6 appears to be U.S.-made, three munitions experts told ABC News.

Journalist Emad Abu Shawiesh captured video of weapons fragments at the UNRWA al Sardi school building in Nuseirat in Gaza on June 6.

The weapon fragments seen in the video are consistent with the nose section of a U.S.-made GBU-39 "Small Diameter Bomb," Trevor Ball, a former U.S. Army explosive ordinance disposal specialist, told ABC News.

The GBU-39 also appeared to have been employed in a deadly strike on May 26 in Rafah, Gaza, according to Ball and another munitions expert, who asked not to be named due to the sensitivity of the issue.

Mark Hiznay, an associate director with the Crisis, Conflict and Arms Division of Human Rights Watch, told ABC News the image shows the remnants of a GBU-39.

N.R. Jenzen-Jones, a director at the consultancy Armament Research Services, said the image was consistent with the Small Diameter Bomb series.

“Given what we know about the IDF arsenal and munitions used in previous strikes, the remnants are most likely from a GBU-39 SDB and include a portion of the nose (forward section) of the bomb,” Jenzen-Jones said, adding that other munitions could have been used in the strike, which he had not yet assessed in detail.

-ABC News Chris Looft