Chris Murphy, a Democrat on the powerful Senate Foreign Relations Committee, stressed that Israel has every right to defend itself from aggression, and that he opposes a ceasefire as it would give Hamas, the Islamist group responsible for the attacks against Israel, time to "regroup."

But "I am concerned that if Israel's strategy and end goal is to defeat Hamas, then this pace of civilian casualties, which certainly comes with a moral cost, also comes with a strategic cost," he told AFP in an interview.

"I think that the civilian death toll has been too high, and a more surgical approach would be important and vital," Murphy said, adding Israel "should be directing the strikes perhaps more so with ground forces than with airstrikes."

Israel is on a mission to destroy Hamas after militants of the Islamist Palestinian group attacked Israel one month ago, killing about 1,400 people, mainly civilians, according to Israeli authorities.

The military's relentless bombardments and ground invasion of Gaza in response has killed more than 10,600 people, also mostly civilians, the Hamas-run Palestinian territory's health ministry has said.

Murphy and more than 20 of his peers sent a letter Wednesday to US President Joe Biden, a fellow Democrat, calling on Israel to "abide by the laws of war," including protection of civilians. 

They also urged Israel to "learn from the mistakes the United States made in our fight against terrorism" two decades ago.

'Creating lots of terrorists' 

Avoiding unnecessary casualties is crucial, Murphy said. But Hamas is also to blame, he said, because the group is "burying itself under civilian institutions, hiding itself in hospitals, schools, and mosques."

Nevertheless, a response that does not limit civilian deaths may create disastrous problems after the war.

"The United States has a lot of experience in fighting terrorist groups like Hamas," according to Murphy.

"What we've learned is that when you are too permissive about civilian deaths, you end up providing bulletin board material to terrorist recruiters and end up killing lots of terrorists, but you end up creating lots of terrorists as well," Murphy said. 

But the senator, who hails from the small northeastern state of Connecticut, next to New York, opposes a ceasefire, as does Biden.

"Hamas made it very clear that they are intent on attacking Israel again and destroying every single Jew they can find," Murphy said. "A ceasefire would allow for Hamas to regroup and start readying their next attack on Israeli civilians."

With a year to go before US presidential elections, concern among some Democrats has swelled that Biden and the party could lose the support of young people, Arab Americans and the country's Muslim minority. 

The United States was the scene this weekend of multiple demonstrations in favor of a ceasefire in Gaza, with some participants holding signs reading "Genocide Joe, You Lost My Vote."

"I don't think you can worry about elections when you're making key decisions about foreign policy and war and peace," Murphy said.