WASHINGTON: US President Joe Biden spoke with Israeli Prime Minister Benjamin Netanyahu on Wednesday as the US administration pursued more aid for its ally and warned that the number of American deaths from the Hamas attack could rise.

White House national security spokesman John Kirby told reporters that the parameters for an additional funding request to Congress had not yet been finalized.

In the near term, Washington can continue to support both Israel and Ukraine as it continues to fight Russia, but "we're certainly running out of runway," he said at a news briefing.

Biden pledged to support Israel after an attack by the Hamas group on Saturday left 1,200 dead and more than 2,700 wounded, according to Israel's count. At least 22 US citizens were among the dead, the State Department confirmed.

Kirby said that the confirmed number of Americans who have died or are being held hostage could rise.

White House in active discussions with Israel over safe passage of civilians from Gaza

"There is no justification for terrorism. No excuse," Biden said during remarks in the Rose Garden, adding that he had again spoken to Netanyahu - his fourth call with the Israeli leader in recent days.

Biden will make more remarks when he meets with Jewish community leaders at the White House later on Wednesday.

In emotional remarks a day earlier, Biden called the attack "an act of sheer evil," and said that US military assistance was being sent to help Israel in its fight.

A person familiar with the matter earlier told Reuters that the White House is weighing a request to Congress that would include military aid to both Israel and Ukraine, which has been fighting Russia's invasion for 20 months.

NBC News on Wednesday reported that the White House is preparing to seek supplemental funding from US lawmakers for those two countries, as well as for Taiwan and US border security.