The US has drafted a new UN security council resolution calling for an “immediate ceasefire” and hostage deal in Gaza, amid mounting pressure on Israel to halt its military campaign and allow the delivery of substantial amounts of humanitarian aid into the Palestinian territory.

The CIA and Mossad spy chiefs, William Burns and David Barnea, were expected to arrive in Qatar on Friday in the hope of clinching an elusive truce-for-hostages deal between Israel and Hamas. Speaking in Egypt, the US secretary of state, Antony Blinken, said difficult work remained to be done but added: “I continue to believe it’s possible.”

Blinken characterised the UN resolution drafted by the US as calling for “an immediate ceasefire tied to the release of hostages.”

If the hostage talks in Doha fail however, the Biden administration will be faced with a dilemma, whether to continue to insist on that linkage in the face of a clear warning this week from a UN panel of experts that a catastrophic famine in Gaza is imminent. The wording of the new US draft resolution presented on Thursday, seen by the Guardian, was more ambiguous than Blinken about the linkage.

It said an “immediate and sustained ceasefire” was “imperative” adding that “towards that end” unequivocal support should be given to the hostage negotiations.

A European diplomat at the UN said the stress on an “immediate” ceasefire and the phrase “towards that end” showed significant movement in the US position. “I think it is a shift in saying that a ceasefire is not contingent on a specific deal,” the diplomat said.

The shift in wording came as European leaders met in Brussels to discuss a common EU call for a ceasefire. The EU foreign policy chief, Josep Borrell, said the failure to get immediate and enough aid into Gaza was a “failure of humanity” and condemned Israel’s reluctance to give full road access to a convoy of trucks waiting with humanitarian aid on the border with Gaza.

But Borrell said he was “happy” that EU member states were being asked to adopt a declaration on Israel that went radically beyond the conclusions in October when they agreed to call for humanitarian pauses in the conflict in the Middle East.

European sources said the change in the US position on a ceasefire may have “allowed Austria and Czechia to revisit their position” and join other member states like Germany in supporting the wording in the draft communique calling for “an immediate humanitarian pause leading to a sustainable ceasefire”.

The change in US language also increases the pressure on the Israeli government, which has been insisting it will carry out a new offensive on the southern Gaza city of Rafah, in the face of strong US objections.

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The hostage talks in Doha will focus on closing a stubborn gap between the negotiating positions of the two parties. Israel has rejected a Hamas proposal for hostage release in exchange for an agreement that would end the war. Israel is focused instead on a temporary pause, in which 40 particularly vulnerable hostages, elderly and sick people and some women, would be freed for a six-week cessation of hostilities.

“I think the gaps are narrowing, and I think an agreement is very much possible,” Blinken told the Saudi news channel Al Hadath. “The Israeli team is present, has authority to reach an agreement.”

Blinken restated US opposition to a planned Israeli offensive on Rafah, the southernmost Gazan city where more than a million Palestinians have take shelter from Israeli bombing.

“A major military operation in Rafah would be a mistake, something we don’t support. And, it’s also not necessary to deal with Hamas, which is necessary,” Blinken told a news conference in Cairo. The Biden administration has invited Israeli officials to Washington to discuss alternatives, a meeting that is expected next week.

The Israeli prime minister, Benjamin Netanyahu, is meanwhile threatening to use his political clout in the US and his close relationship with the Republican Party to resist pressure from the administration. Netanyahu held a 45-minute call with Republican senators on Wednesday, in which he vowed to press ahead with a Rafah operation. The Republican House Speaker, Michael Johnson, said he intended to invite the Israeli leader to address a joint session of Congress, which would be an echo of Netanyahu’s previous appearance in 2015, when he used it as a platform to voice opposition to Barack Obama’s Middle East policies.

Pressure is also piling up on Biden from the other direction, pressing for an unconditional ceasefire. In a letter to the president, 67 former US national security officials urged him to press for a truce.

“Civilian killings of this nature and magnitude cannot be justified,” the letter said. We are also concerned that Israeli conduct of the war risks making Gaza uninhabitable for Palestinians.”

The US draft resolution is unusually detailed, containing 26 operative paragraphs, stressing the demand for “the immediate, safe, sustained and unhindered delivery of humanitarian assistance at scale directly to the Palestinian civilian population throughout the Gaza Strip”.

Details of the draft resolution were revealed as the UN released an analysis of satellite imagery showing that 35% of buildings in Gaza had been damaged or destroyed during Israel’s offensive, which has claimed almost 32,000 Palestinian lives.

The US has vetoed previous UN security council votes on the nearly six-month-long war, objecting as recently as in February to the use of the term “immediate” in a draft submitted by Algeria. In recent weeks, however, Washington has upped the pressure on its ally while insisting Hamas militants must immediately release the hostages seized during its 7 October attacks on Israel.

US officials had been negotiating an alternative text since blocking the Algerian draft resolution calling for an “immediate humanitarian ceasefire” in Gaza at the end of February. That alternative, focusing on support for a six-week truce in exchange for the release of hostages, had little chance of winning approval, according to diplomatic sources.

While no vote has yet been scheduled on the new text, it sends the clearest message yet to Israel of the Biden administration’s growing frustration with its prosecution of the war, and comes after a warning from the UN human rights chief, Volker Türk, that Israel may be committing a war crime by using “starvation as a method of war”.