"This is a difficult and very disappointing statement to hear from a president to whom we have been grateful since the beginning of the war," Israel's ambassador to the United Nations, Gilad Erdan, said on public radio in Israel's first reaction to Biden's warning.

Israel has defied international objections by sending in tanks and conducting "targeted raids" in the eastern areas of Rafah.

It says Rafah is home to Hamas's last remaining battalions but the city on the border with Egypt is also crammed with displaced Palestinian civilians.

"If they go into Rafah, I'm not supplying the weapons that have been used... to deal with the cities," Biden told CNN, in his starkest warning to Israel since the start of the war.

"Civilians have been killed in Gaza as a consequence of those bombs," Biden said. "It's just wrong."

Erdan said Biden's comments would be seen by Israel's foes Iran, Hamas, and Hezbollah as "something that gives them hope to succeed".

"If Israel is restricted from entering an area as important and central as Rafah where there are thousands of terrorists, hostages and leaders of Hamas, how exactly are we supposed to achieve our goals?" he said.

"This is not a defensive weapon. This is about certain offensive bombs. In the end the State of Israel will have to do what it thinks needs to be done for the security of its citizens."

Israel's far-right Finance Minister Bezalel Smotrich said his government would pursue its goals in Gaza despite the US threat.

"We will achieve complete victory in this war despite President Biden's push back and arms embargo," he said in a statement.

"We must continue the war until Hamas is totally eliminated and our hostages are back home. This involves conquering Rafah completely and the sooner the better."

- 'We will stand strong' -

AFP journalists reported heavy shelling in Rafah early Thursday, and the Israeli military later said it was also striking "Hamas positions" further north in the centre of the Gaza Strip.

On Tuesday, Israeli forces seized Rafah's border crossing into Egypt, which has served as the main entry point for aid into besieged Gaza.

In a separate address that appeared to be directed at Biden, Israel's Defence Minister Yoav Gallant also vowed to continue the fight.

"I turn to Israel's enemies as well as to our best friends -- the State of Israel cannot be subdued, not the IDF (army, not the defence establishment," Gallant said in an address at a ceremony.

"We will stand strong, we will achieve our goals. We will hit Hamas, we will hit Hezbollah, and we will achieve security."

Since the war in Gaza broke out on October 7, Israeli forces have been also engaged in near-daily clashes with Lebanon's Iran-backed Hezbollah fighters along the border between the two countries.

Hezbollah began attacking Israel in support of ally Hamas a day after the Palestinian militant group's unprecedented October 7 attack on Israel that sparked war in the Gaza Strip.

In recent weeks Hezbollah has stepped up its attacks, while Israel's military has struck deeper into Lebanese territory.

At least 399 people have been killed in Lebanon in seven months of cross-border violence, mostly militants but also including more than 70 civilians, according to an AFP tally.

Israel says 14 soldiers and nine civilians have been killed on its side of the border, including one on Wednesday.

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