The UK and the US took a “joint decision” to keep Kabul airport’s Abbey Gate open last Thursday, British sources have said, despite what turned out to be a prophetic warning that a terror attack by Islamic State Khorasan Province (ISKP) on western soldiers and gathering crowds was imminent.

The fresh briefing comes in the aftermath of an unusually detailed leak of the run-up to Thursday’s deadly bombings, which had claimed that the Americans had kept the gate “open longer than they wanted to” so the UK could finish its evacuation from Afghanistan.

British defence sources in effect disputed the leaked account, arguing in a fresh briefing that both countries’ militaries had agreed to keep the Abbey Gate open, in what was described by the UK as a “joint decision” despite the acknowledged risk.

More than 170 Afghans and 13 US marines were killed in a double bomb attack at the Abbey Gate and the nearby Baron hotel, also being used by British officials. Responsibility for the atrocity was claimed by ISKP, the Afghan affiliate of the global terror group.

Over the weekend, Politico reported on the US military’s thinking in the run-up to the attack, in which senior officials discussed on Wednesday in Washington how to prepare for what they feared was an imminent “mass casualty event”.

Commanders had concluded that the Abbey Gate was potentially the highest risk location, but it was nevertheless kept open because it was being used by the British to conclude an already accelerated evacuation.

According to notes of meetings obtained as part of the leak, R Adm Peter Vasely, the commander of US forces in Afghanistan, told senior colleagues that the Abbey Gate, was not closed on Thursday afternoon Kabul time as had been planned.

If accurate, that would imply the decision was not necessarily consensual, as the new British account suggests.

Earlier on Tuesday, the UK foreign secretary, Dominic Raab, also rejected US claims that Britain was indirectly responsible for the suicide attacks at Kabul airport last week because it insisted that the Abbey gate entry point to the site be kept open to allow British nationals to enter the airport.

The British minister said in a radio interview that the “story was simply untrue”, adding nothing the UK did required Abbey gate to be kept open that day.

“We co-ordinated very closely with the US, in particular around the Isis-K [ISKP] threat, which we anticipated although tragically were not able to prevent, but it is certainly right to say we got our civilians out of the processing centre by Abbey gate, but it is just not true to suggest that other than securing our civilians inside the airport that we were pushing to leave the gate open,” Raab said.

On Monday, prior to Raab’s comments, the UK was briefing it had nothing substantive to say about the Politico report, which was widely followed up.

The foreign secretary’s statement and revised briefing demonstrate that British politicians and its military recognise the seriousness of the story required them to provide a fuller version of events.