Any move by Israel to occupy the Gaza Strip again would be a "big mistake," US President Joe Biden said in an interview released on Sunday, as Israeli troops prepared for a ground invasion.

Israel, seeking vengeance for an attack by Hamas on 7 October, has declared war on the militant group, launching a relentless bombing campaign and warning more than a million people in northern Gaza to move south ahead of the operation.

Asked by CBS news program "60 Minutes" if he would support any occupation of Gaza by the American ally, Biden replied: "I think it'd be a big mistake."

Hamas "don't represent all the Palestinian people," he continued.

But invading and "taking out the extremists" is a "necessary requirement," he added.

The Hamas attack saw fighters shoot, stab, and burn to death more than 1,400 people, most of them civilians. Israel's reprisal attacks in the days since have flattened neighborhoods and killed at least 2,670 people in Gaza, the majority ordinary Palestinians.

Israel has faced grave warnings about the implications of putting boots on the ground in Gaza, with aid groups warning of a humanitarian disaster, fears of the conflict escalating, and the challenges of separating militants from civilians in the impoverished, densely occupied territory.

Israel first occupied Gaza during the 1967 Six-Day War, and it was only fully returned to Palestinians in 2005.

A year later, Israel imposed an air, land, and sea blockade on the 140 square mile (362 square kilometers) strip of land, which is also bordered by Egypt and the Mediterranean Sea.

In 2007 Israel tightened the blockade after Hamas took control of Gaza from the secular Fatah movement of Palestinian President Mahmud Abbas.

When asked if Hamas — whom Biden described as "a bunch of cowards" — must be eliminated entirely, he replied: "Yes I do."

"But there needs to be a Palestinian authority. There needs to be a path to a Palestinian state," he continued, reiterating the long-standing US call for a two-state solution.