WASHINGTON (Reuters) - U.S. Secretary of State Antony Blinken on Sunday defended a decision to pause a delivery to Israel of 3,500 bombs over concerns they could be used in the Gazan city of Rafah, saying Israel lacked a "credible plan" to protect some 1.4 million civilians sheltering there.

Speaking to ABC News' This Week, Blinken said that President Joe Biden remains determined to help Israel defend itself and that the shipment of 3,500 2,000-pound and 500-pound bombs was the only U.S. weapons package being withheld.

That could change, he said, if Israel launches a full-scale attack on Rafah, which Israel says it plans to invade to root out fighters of the ruling Hamas militant group.

Biden has made clear to Israel that if it "launches this major military operation to Rafah, then there are certain systems that we're not going to be supporting and supplying for that operation," said Blinken.

"We have real concerns about the way they're used," he continued. Israel needs to "have a clear, credible plan to protect civilians, which we haven't seen."

Rafah is hosting some 1.4 million Palestinians, most of them displaced from elsewhere in Gaza by fighting and Israeli bombardments, amid dire shortages of food and water.

The death toll in Israel's military operation in Gaza has now passed at least 35,000 Palestinians, according to Gaza's Hamas-run health ministry.

The war was triggered by the Hamas-led attack on southern Israel on Oct. 7 in which some 1,200 people were killed and more than 250 people taken hostage, according to Israeli tallies.

Israel says 620 soldiers have been killed in the fighting.

(Reporting by Jonathan Landay; Editing by Josie Kao)