Nancy Pelosi among Democrats urging Joe Biden to halt weapons ...

More than three dozen congressional Democrats – including representative Nancy Pelosi, the former House speaker and a key Joe Biden ally – signed a letter to the US president and the secretary of state Antony Blinken, urging a halt to weapons transfers to Israel.

“In light of the recent strike against aid workers and the worsening humanitarian crisis, we believe it is unjustifiable to approve these weapons transfers,” the letter said. It was signed by Pelosi and 36 other Democrats including representatives Barbara Lee, Rashida Tlaib and Alexandria Ocasio-Cortez.

Friday’s letter also calls on the US to withhold future arms transfers pending a US investigation into the air strike on the World Central Kitchen humanitarian workers or if Israel “fails to sufficiently mitigate harm to innocent civilians in Gaza”.

It comes as Biden on Friday wrote to the leaders of Egypt and Qatar, calling on them to press Hamas for a hostage deal with Israel, according to a senior administration official.

The official, who spoke on the condition of anonymity to discuss the private letters, said Biden’s national security adviser will meet on Monday with family members of some of the estimated 100 hostages who are believed to still be in Gaza.

The letters, to Egyptian president Abdel Fattah el-Sisim and Qatar’s ruling emir, Sheikh Tamim bin Hamad Al Thani, come as Biden has deployed CIA Director Bill Burns to Cairo for talks this weekend about the hostage crisis.

White House officials said negotiating a pause in fighting between Israel and Hamas to facilitate the exchange of hostages held in Gaza for Palestinian prisoners held in Israel is the only way to put a temporary ceasefire into effect and boost the flow of badly humanitarian aid into the territory.

On Thursday, hours after Biden told Israel to take concrete steps to protect civilians and aid workers in Gaza or risk losing military support from the US, top senators belonging to the president’s Democratic Party ramped up pressure on the White House to go further.

The progressive senator Bernie Sanders was among the strongest voices. “Israel should not be getting another nickel in military aid” until it markedly facilitates the flow of provisions into a region that the US suspects is already grappling with famine, he said.

“We are looking at one of the worst humanitarian disasters that we have seen in a very, very long time … because Israel is not allowing the humanitarian trucks into Gaza, and especially into the areas where people are in most desperate condition,” Sanders told CNN on Thursday.

[ ‘They are heroes to us’: The seven aid workers killed in Monday’s Israeli air strike ]

Adding that it was not the US’s job to worry about how Gaza may tie into the political future of the Israeli prime minister, Binyamin Netanyahu, the Vermont senator added: “My view is no more military aid to Israel when children [there] are starving.”

Meanwhile, the Democratic senator Chris Van Hollen of Maryland insisted that the president enforce a national security memorandum signed in February that aimed to condition the transfer of military weaponry to Israel on its adherence to humanitarian benchmarks.

“I was glad to see the president indicate that he’s going to monitor compliance and base US policy going forward on the government meeting these requirements,” Van Hollen told Politico Playbook. “That suggests no more ‘anything goes’ when it comes to policies towards the Netanyahu government.”

Topping the list of policies that Biden could leverage against Israel is the suspension of transferring “offensive weapons” to Israel if it fails at “reducing civilian harm” or “getting desperately needed assistance to people in need”, Van Hollen said. The senator alluded to that policy days after Israeli air strikes killed seven employees of the international food charity World Central Kitchen (WCK). Following the attack, a cargo ship carrying 240 tonnes of food destined for Gaza returned to Cyprus.

The Massachusetts Democratic senator Elizabeth Warren said she would seek to impede the sale of F-15s to Israel after the killings of the WCK staffers, which included a US-Canadian citizen and three British nationals.

On Thursday, top senators belonging to Joe Biden's Democratic Party ramped up pressure on the White House to go further. Photograph: Samuel Corum/AFP

A day before the WCK workers were killed, a report surfaced that the Biden administration was mulling an $18 billion (€16.6 billion) arms transfer package to Israel that would include more than two dozen F-15 fighter jets.

“We cannot approve the sale of arms to a country that is in violation of our own laws on this,” Warren told CNN. “And that includes access to humanitarian relief.

“This is a moral question – it is also a legal question. Congress has responsibility here, and I’m willing to take that responsibility.”

Netanyahu has said Israel killed the WCK staffers unintentionally, and two senior military officers have been fired as a result.

Sanders, Van Hollen and Warren are all part of a 51-49 majority that Democrats – and independents who caucus with them – hold in the Senate.

[ Biden’s approach to Israel has a newfound urgency ]

Biden and his administration have generally stood in steadfast support of Israel, which has struck Gaza on land and by air after the October 7th attack by Hamas killed 1,100 Israelis and also took hostages. But with the death toll in Gaza climbing above 30,000 and the humanitarian crisis worsening, the US – which provides Israel with at least $3.8 billion in security assistance annually – recently abstained from a United Nations vote which resulted in a resolution demanding an immediate ceasefire in Gaza.

Biden on Thursday for the first time called for an immediate ceasefire, too. – Guardian/AP