(CNN) — Top American officials offered stark warnings Sunday against an Israeli invasion of Rafah, predicting that a major ground offensive in the southern Gaza city would lead to widespread civilian casualties, spark a Hamas insurgency and create a power vacuum the terror group would later seek to fill.

The alarm bells from US Secretary of State Antony Blinken and White House national security adviser Jake Sullivan came after President Joe Biden delivered an ultimatum last week on CNN that an Israeli invasion of Rafah would cause him to pause certain weapons transfers.

Blinken and Sullivan both said Biden made the determination because he didn’t want American weapons used in what he estimates would be a bloody, ill-advised operation.

At the same time, they sought to rebut claims from Republicans and pro-Israel Democrats that Biden was leaving Israel to fend for itself. And Blinken worked to explain why his agency last week was unable to make a full determination on whether Israel was upholding international law in its campaign against Hamas, a conclusion that drew criticism from human rights groups and some lawmakers.

Blinken said on Sunday that the US believes Israel has killed more civilians than Hamas terrorists as part of its war in Gaza, and that Israel needs to do more to mitigate civilian deaths.

“While Israel has processes, procedures, rules, regulations to try to minimize civilian harm, given the impact that this operation, this war in Gaza has had on the civilian population, those have not been applied consistently and effectively,” Blinken said on CBS’ “Face the Nation.”

The Ministry of Health in Gaza reported Sunday that the number of people killed in the enclave as a result of Israeli military operations has risen above 35,000.

Despite American warnings dating back months about the wisdom of a ground invasion into Rafah, Israel appears poised to continue advancing on the city and has issued evacuation orders for some of the 1.4 million civilians estimated to be sheltering there.

Going “headlong into Rafah” could have dire consequences, Blinken warned Sunday.

“Israel’s on the trajectory, potentially, to inherit an insurgency with many armed Hamas left, or, if it leaves, a vacuum filled by chaos, filled by anarchy and probably refilled by Hamas,” Blinken said Sunday on NBC’s “Meet the Press.”

Sullivan, meanwhile, warned an Israel operation would cause “really significant civilian casualties” while still being unlikely to eliminate Hamas.

That is partly why Biden determined that American weapons should not be used in a Rafah offensive.

“He doesn’t want to see American weapons used in that kind of operation,” Sullivan said Sunday on ABC’s “This Week.”

“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.”

Sullivan on Sunday spoke by phone with his Israeli counterpart, Tzachi Hanegbi, and “reiterated President Biden’s longstanding concerns over the potential for a major military ground operation into Rafah,” the White House said.

“Mr. Hanegbi confirmed that Israel is taking US concerns into account,” according to a White House readout of the call.

Blinken said Israel had resisted American advice for developing a plan for Gaza once the war ends.

“We’ve been working for many, many weeks on developing critical plans for security, for governance, for rebuilding. We haven’t seen that come from Israel, we’ve been working with Arab countries and others on that plan. We need to see that too. We have the same objective as Israel. We want to make sure that Hamas cannot govern Gaza again,” he told CBS.

Last week, the State Department released a report finding it is “reasonable to assess” that US weapons have been used by Israeli forces in Gaza in ways that are “inconsistent” with international humanitarian law. But the report stopped short of officially saying Israel violated the law.

“We don’t have double standards. We treat Israel, one of our closest allies and partners, just as we would treat any other country,” Blinken said on NBC.

Still, he said making such a full determination was impossible amid the war.

“That makes it very difficult to determine, particularly in the midst of war, exactly what happened and to draw any final conclusions from any one incident,” Blinken told CBS.

The top US diplomat downplayed a growing rift between Biden and Israeli Prime Minister Benjamin Netanyahu, even as the relationship endures its tensest moment since Hamas’ October 7 attacks.

“We are clear-eyed, and we speak the truth to each other as we see it,” Blinken said. “We have American interests first and foremost in mind. We also have Israel’s interests in mind. And there may be a difference in view and in the best way to achieve them. But that’s also the nature of the relationship.”

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