Sullivan: Pause in military aid doesn't mean Biden will 'abandon Israel'

White House national security adviser Jake Sullivan on Sunday maintained President Biden's threat to withhold offensive weapons from Israel does not mean the U.S. intends to "abandon" Israel.

Sullivan, speaking with ABC News anchor George Stephanopoulos, warned of "significant" civilian casualties in the southern Gaza city of Rafah. It comes days after President Biden threatened to withhold offensive weapons from Israel if they launch a full-scale invasion of the city.

"Well, first, because there is a million people there's a million people there in very close quarters who've been pushed there, because of the military operations and other parts of Gaza, you would have really significant civilian casualties," Sullivan said in an interview released Sunday. "And while Israel would also be able to kill some Hamas folks, many Hamas folks would melt away because they're terrorists. They're not really organized fights in the way that we think about a typical military in that context."

"He [Biden] doesn't want to see American weapons used in that kind of operation. That's not to say that he is going to abandon Israel or cut them off from weapons. He was focused on a particular operation that he doesn't believe will succeed in defeating Hamas and that will cause grievous harm," he added.

Biden's warning over Rafah is facing blowback from some Republicans and Israeli leaders who contend moving into the city is necessary to eliminate Hamas forces there.

The White House for weeks has cautioned Israeli Prime Minister Benjamin Netanyahu against a full-scale incursion while the city is being used as a refuge by more than a million civilians.

Israel ordered new evacuations in the southern city over the weekend.

Biden has become increasingly critical of Israel's wartime campaign and has upped pressure on Netanyahu and other Israeli leaders to take more caution in preventing civilian deaths.

More than 35,000 Palestinians have died in Gaza since the conflict began in early October, when Hamas forces launched a surprise assault on Israel that killed about 1,200 people.

"Nobody has been a stronger supporter of Israel than Joe Biden. He has sent an enormous amount of capability for Israel to take on Hamas," Sullivan said. "Secondly, the president has made clear he's going to continue to make sure Israel has what it needs to defend itself. Full stop, for square that will happen."

"And then third, the president has said that he has concerns about a full-scale military invasion of Rafah, a place where there's more than a million people sheltering with nowhere else to go," he continued.

In an interview with NBC News's "Meet the Press" on Sunday, Secretary of State Antony Blinken said the U.S. has not seen "credible plans" from Israel on preventing civilian deaths in Rafah.

"We also haven't seen a plan for what happens the day after this war in Gaza ends, because right now, the trajectory that Israel is on is, even if it goes in and takes heavy action in Rafah, there will still be thousands of armed Hamas left," Blinken said.