Joe Biden has defended the US military pullout in Afghanistan, saying that the mass evacuation of refugees would have been “hard and painful no matter when we started”.

The US president said “my heart aches” for the thousands who are stranded outside Kabul airport in desperate scenes, but added that it was “just a fact” that the evacuation would have been difficult no matter how or when it was planned.

Tony Blair is among many who have criticised Mr Biden for the chaos seen in Kabul and across Afghanistan, with the former prime minister saying that the decision to withdraw troops was “imbecilic”.

At a White House news conference, Mr Biden said he had a “basic decision to make” and was “convinced I’m absolutely correct in not sending more men and women to war”.

He said: “If we do not leave Afghanistan now, when do we leave?”

Mr Biden added that he would not like to extend his deadline to stop evacuations and withdrawn US forces from Kabul on 31 August, but that talks were ongoing over this.

Afghans are becoming more desperate as the end of August approaches, with the last civilian flight to leave some time before that.

Mr Biden reiterated that his first priority is getting American citizens out of Afghanistan “as quickly and safely as possible”, adding that 11,000 individuals were evacuated over the weekend.

But ministers want Mr Biden to keep American forces on the ground beyond that date, with Labour calling for the prime minister to phone the UK ally to extend the exit date.

Boris Johnson confirmed on social media that he will convene G7 leaders, which will include Mr Biden, on Tuesday for “urgent talks” on the situation in the country.

And in a statement, White House press secretary Jen Psaki said the group would discuss “continuing our close co-ordination on Afghanistan policy” as well as ongoing evacuation efforts.

The Ministry of Defence (MoD) confirmed on Sunday that seven Afghan civilians had died in chaotic crowds outside Kabul airport, however reports have suggested as many 20 people have been killed in the past week while trying to get into the airfield.

Today, Sky News chief correspondent Stuart Ramsay witnessed UK armed forces working with the Taliban to restore order and process more evacuees but serious safety risks remain.

Former chief of the defence staff Lord Richards said UK forces securing the air strip are in a “very precarious situation”, with little protection from security threats posed by the likes of so-called Islamic State.

“I’ve done a few of these non-combat evacuation operations in my time and this is the worst possible scenario, when you are unable to clear a space between the airhead and your possible threat, which is exactly what is happening now,” he told Times Radio.

Armed forces minister James Heappey said British troops are “seeing things that are unimaginably hard to deal with”, with reports of overcrowding, violence and shortages in the Kabul heat.

However, he said there have been “very encouraging” improvements at the Baron Hotel in the city, where Britons and Afghans eligible for repatriation are being processed, following reports earlier this weekend that it had been blockaded by the Taliban.

He said the “flow” outside the hotel is “significantly” better following changes to crowd control by the militant regime, with 731 people processed for UK flights on Sunday morning alone.