Senior ministers and officials will hold an emergency Cobra meeting today as thousands of British nationals remain trapped in Sudan.
The crunch summit will take place in Whitehall as plans are drawn-up to rescue at least 2,000 UK citizens stuck in the war-torn country.
The Prime Minister’s spokesman said: “We will pull every lever possible to help bring about a ceasefire and equally to support British nationals.”
He added: “We are working round the clock to support those who are remaining.”
One estimate said up to 4,000 UK citizens could be stranded in the African nation amid deadly street fighting and a shortage of food, water and electricity.
Some said they felt "abandoned" after diplomats were rescued in a night-time evacuation mission and were organising dangerous private evacuations.
Foreign Office Minister Andrew Mitchell said the Government was doing "everything we can" to get British nationals out, but dampened hopes of it happening before a ceasefire.
He defended the prioritisation of embassy staff, saying there had been "a very specific threat to the diplomatic community" in the capital Khartoum.
Alicia Kearns, the Tory chairwoman of the Commons Foreign Affairs Select Committee, called for the focus to shift to getting UK civilians out "because there is no imminent sign of a ceasefire".
She estimated there could be "3,000, 4,000 plus" British nationals trapped in Sudan.
Ms Kearns said Britons in Sudan will be in "abject fear", with reports of some people killing their pets "because they're worried they're going to starve".
"The reality is we have to get British nationals out,” she said.
“If, however, there was to be no evacuation because it's too dangerous ... then we have a moral obligation to tell British nationals as soon as possible that that is the judgment that has been made because they then need to be able to make their own decisions."
Meanwhile, other nations have rushed to get their citizens out.
The European Union's foreign policy chief Josep Borrell said more than a thousand people have been extracted through the combined efforts of member states.
Around 50 Irish citizens have been evacuated from Khartoum to Djibouti with the support of France and Spain, with more evacuations planned, deputy premier Micheal Martin said.
Commons Defence Select Committee chairman Tobias Ellwood called for a "clear-cut plan" to get British passport-holders out of Sudan.
"If that plan does not emerge today, then individuals will then lose faith and then start making their own way back," he told GB News, saying that could lead to "some very difficult situations".
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