U.S. national security adviser Jake Sullivan said on Monday that President Joe Biden's administration did not view the killings of Palestinians in Gaza by Israel in its war with Hamas as a genocide.

Sullivan, speaking to reporters at the White House, said the United States wants to see Hamas defeated, that Palestinians caught in the middle of the war were in "hell," and that a major military operation by Israel in Rafah would be a mistake.

"We do not believe what is happening in Gaza is a genocide. We have been firmly on record rejecting that proposition," Sullivan said.

Biden, who is running for reelection this year, has faced heavy criticism from his own supporters domestically for his support of Israel; some of those critics have accused Israel of committing genocide. More than 35,000 Palestinians in Gaza have died, according to Gaza health officials.

Reiterating a comment Biden made on Saturday, Sullivan said there could be a ceasefire in Gaza now if Hamas would release hostages. The world should be calling on Hamas to return to the negotiating table and accept a deal, Sullivan said.

The United States is working urgently for a ceasefire and hostage release deal, Sullivan said. He said he could not predict when or if such a deal would be sealed.