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

Centrist Israeli minister Benny Gantz announced Sunday that he was resigning from the emergency government because of what he has described as a lack of a plan from Israeli Prime Minister Benjamin Netanyahu for the "day after" in Gaza.

During a televised news conference, Gantz announced he was resigning from the coalition government, taking with him his State Party and the seats it held in the Knesset. Netanyahu's coalition government will still retain a majority, but the move by Gantz is considered a major blow to the prime minister.

"Netanyahu is preventing us from progressing towards a true victory," Gantz said. "For this reason, we are leaving the emergency government today, with a heavy heart, yet wholeheartedly."

He also called on Netanyahu to set a date for elections.

Gantz was set to make the announcement on Saturday but called it off amid the news of an Israel Defense Forces operation in Gaza that led to the rescue of four Israeli hostages.

Gantz is a member of Israel’s three-member war Cabinet, which includes Netanyahu and Defense Minister Yoav Gallant.

On Saturday, Netanyahu appealed to Gantz on X, saying, "This is the time for unity and not for division. We must remain united within ourselves in the face of the great tasks before us. I call on Benny Gantz -- do not leave the emergency government. Don't give up on unity."

Following Gantz's resignation, Netanyahu released a statement on X, saying, "Israel is in an existential war on several fronts."

"Benny, this is not the time to abandon the campaign -- this is the time to join forces," Netanyahu said. "Citizens of Israel, we will continue until victory and the achievement of all the goals of the war, primarily the release of all our hostages and the elimination of Hamas."

Netanyahu added, "My door will remain open to any Zionist party that is ready to get under the stretcher and assist in bringing victory over our enemies and ensuring the safety of our citizens."

In May, Gantz issued an ultimatum to Netanyahu, saying he would resign if the prime minister did not approve a post-war plan by June 8, saying at the time, "While the Israeli soldiers show supreme bravery on the front, some of the men who sent them into battle behave with cowardice and irresponsibility."

-ABC News' Jordana Miller