Boris Johnson cut short his UK tour on Monday to return to London as western leaders voiced concerns a Russian invasion of Ukraine could happen imminently, and Liz Truss convened a Cobra meeting to discuss the UK’s consular response. The foreign secretary will consider whether to change advice to UK diplomats in the country, after it issued new guidance on Friday advising British citizens in Ukraine to leave immediately while commercial flights are still available. Number 10 said Johnson would receive an intelligence briefing on his return to London, having been due to visit Cumbria, and will convene another full Cobra meeting on Tuesday. Speaking on a visit to Scotland, Johnson said he would be making immense diplomatic efforts over the coming days including liaising with the US president, Joe Biden. He said that Ukraine’s future membership of Nato could not be “bargained away” as part of western leaders’ efforts. “I think it’s very important that we have a conversation, but what we can’t do is trade away the sovereign rights of the Ukrainians who aspire to Nato membership,” he said. “That’s something that was a massive gain for our world. If you remember what happened in 1990, you had a Europe whole and free, countries could decide their own futures. We can’t bargain that away. It’s for the Ukrainian people.” Parliament could be recalled if Russia invades Ukraine this week, Number 10 indicated. Asked if this was a possibility, the PM’s official spokesman said: “In that situation you would expect that the prime minister would want parliament to be updated and for it to have its say.” Johnson’s spokesman said there was no indication at the moment that diplomatic efforts would halt the invasion. “It’s certainly true that we have seen no sign so far that Russia will back down. There are more than 130,000 Russian troops on the border with Ukraine and we are gravely concerned. But we will continue to explore every possible avenue to talk Russia back from this path.” The UK ambassador to Ukraine, Melinda Simmons, had said she will remain in Kyiv with a core team of diplomats. Many western nations have advised their citizens to evacuate. The US and Canadian embassies have told non-essential staff and family members to return home while others will work from the western Ukrainian city of Lviv. The German chancellor, Olaf Scholz, visited Kyiv on Monday and will travel to Moscow on Tuesday, warning that an attack by Russia would lead to “tough sanctions that we have carefully prepared and which we can immediately put into force”. Downing Street said British nationals should not expect a “military airlift” from Ukraine. “British nationals should leave Ukraine via commercial means and there are still flights available,” Johnson’s spokesman said.