Fifteen Israeli soldiers were killed in combat in the Gaza Strip over the weekend, the Israeli military said Sunday.

Israeli Prime Minister Benjamin Netanyahu called the fatalities a "very heavy price."

This weekend’s fatalities bring the total number of Israeli soldiers killed since the ground offensive began to 153, the Israel Defense Forces said.

Israel is "deepening the war" in Gaza, and Israeli soldiers "will continue to fight until the complete victory over Hamas," Israeli Prime Minister Benjamin Netanyahu said in an address Sunday.

"This is the only way to return our abductees, eliminate Hamas and ensure that Gaza will no longer be a threat to Israel," Netanyahu said. "It will take time, but we are united -- the fighters, the people and the government."

President Joe Biden said he did not ask for a cease-fire during a call earlier Saturday with Israeli Prime Minister Benjamin Netanyahu.

"I had a long talk with Netanyahu today. It was a private conversation," he told reporters while leaving the White House for Christmas at Camp David.

He later said, "I did not ask for a cease-fire."

The leaders discussed Israel's military operation in Gaza, the humanitarian crisis in Gaza and securing the release of the remaining hostages, according to a readout of the call released by the White House. The two agreed to remain in "regular consultation," the readout stated.

Biden also did not respond to questions about a new Wall Street Journal report that in the days after the Oct. 7 attack he convinced Netanyahu against a preemptive strike on Hezbollah forces in Lebanon.

ABC News has not confirmed the report.

-ABC News' Lauren Peller and Jay O'Brien

Gadi Hagi, a 73-year-old American-Israeli hostage and member of Kibbutz Nir Oz, has been confirmed dead, the kibbutz said.

Hagi was killed on Oct. 7 at the kibbutz and his body was taken to Gaza where it's still being held, according to a kibbutz spokesperson.

Hagi’s wife, 70-year-old Judy Weinstein, is wounded and still being held hostage, the kibbutz said.

Hagi and his wife were shot and kidnapped on Oct. 7, according to the Hostage Center.

"Gadi was a man full of humor who knew how to make those around him laugh," the Hostage Center said in a statement. "A musician at heart, a gifted flautist, he played in the IDF Orchestra and was involved with music his whole life."

Hagi was a father of four and a grandfather of seven.

Hagi reportedly has ties to New York.

"May Gadi's memory be a blessing," New York Gov. Kathy Hochul wrote on social media. "There are still many hostages -- including many with New York connections -- being held in Hamas captivity."

President Joe Biden said he was "heartbroken by the news."

"We continue to pray for the well-being and safe return of his wife, Judy," Biden said in a statement. "We are praying for their four children, seven grandchildren, and other loved ones and are grieving this tragic news with them."

Biden said Hagi's daughter joined, via phone, his meeting last week with families of hostages.

"Those families bravely shared with me the harrowing ordeal that they have endured over the past months as they await news of their loved ones," Biden said. "I reaffirm the pledge we have made to all the families of those still held hostage: we will not stop working to bring them home."

The Israel Defense Forces has published the findings of its investigation into the accidental killing of three hostages by IDF soldiers in the Shejaiya area of Gaza on Dec. 15.

The IDF Chief of the General Staff concluded that "the IDF failed in its mission to rescue" them and "the entire chain of command feels responsible."

The three hostages -- 28-year-old Yotam Haim, 26-year-old Alon Shamriz and 22-year-old Samer Talalka -- were carrying a stick with a white cloth, and the IDF initially said its forces "mistakenly identified" the men as a threat. Soldiers opened fire, killing two of the men.

The third hostage, who was injured, ran back into the building where all three had emerged from, and someone cried "help" in Hebrew. The battalion commander ordered his troops to stop firing, but, despite the order, another burst was fired, killing the third hostage, according to the IDF.

The investigation “revealed that the command ranks had information about the presence of hostages in the Shejaiya area and even took actions to prevent strikes on locations suspected of having hostages inside," the findings said.

But the probe also revealed that "IDF soldiers involved in the incident experienced complex combat situations in the days preceding the incident and were in a state of high alert for a threat," the findings said. "During the battles, they encountered deceptions by the enemy and attempts to draw them into pits and buildings rigged with explosives."

Days before Dec. 15, IDF soldiers heard cries for help in Hebrew.

"The forces interpreted this as a terrorist deception attempt," the investigation said.

“Some of the forces heard the cries but suspected it was an attempt by the terrorists to draw the forces inside the building to harm them, as had happened in the past," the investigation said.

-ABC News’ Jordana Miller