Boris Johnson is to issue an appeal for Nato unity amid increasing strains within the Western alliance over the conflict in Syria.
The Prime Minister will break off from the election campaign to host a gathering of Nato leaders in Britain marking the alliance’s 70th anniversary.
Their talks take place amid a bitter row between French President Emmanuel Macron and Turkish President Recep Tayyip Erdogan over Turkey’s recent incursion into northern Syria.
Mr Macron infuriated Ankara when he suggested Nato was suffering from “brain death” over the lack co-ordination over Turkey’s “crazy” attack on the Kurds, seen as a key Western ally in the fight against so-called Islamic State.
The Turkish president, who has long sought a free hand against the Kurds, hit back accusing Mr Macron of “a sick and shallow understanding” of terrorism, suggesting he was the one who was “brain dead”.
Mr Johnson is expected to try to play peacemaker when he hosts the two leaders, together with German Chancellor Angela Merkel, for talks in Downing Street on Tuesday ahead of the main gathering.
The Prime Minister’s official spokesman said: “The PM’s position is that Nato is the most enduring and successful alliance in military history and that it continues to adapt to the evolving threats that we face.
“It is the cornerstone of Euro-Atlantic security and it helps to keep a billion people safe.
“The PM will emphasise that all members must be united behind shared priorities so Nato can adapt to the challenges ahead.”
The meetings comes after Mr Johnson, Mr Macron and Mrs Merkel all sought to raise the issue of Turkey’s incursion last October across the border into Kurdish-controlled areas of northern Syrian.
The invasion took place after Donald Trump effectively gave the Turkish president the green light – to the dismay of other Western capitals as well as many in Washington.
It was widely seen to have strengthened both the Russian position in Syria and that of the Assad regime – who the Kurds were forced to turn for help – while triggering a fresh humanitarian crisis.
There was further alarm in among alliance members when Mr Erdogan chose to to purchase Russian air defence systems – seen as a further weakening of his commitment to the alliance.
Mr Trump is also among the Nato leaders attending the two-day gathering.
At past meetings, he has berated European leaders for failing to contribute more financially to the costs of collective defence.
Meanwhile, Downing Street will be hoping the US president does not decide to intervene in the general election campaign in such a way as to rebound against Mr Johnson.
Mr Trump has previously urged the Prime Minister to form an alliance with Brexit Party leader Nigel Farage while warning that Jeremy Corbyn would take Britain to “bad places”.
Mr Johnson said last week that “close friends and allies” like the UK and the US should not get involved in each other elections.
The formal Nato events will begin with a reception at Buckingham Palace hosted by the Queen on Tuesday evening.
The main talks will then take place on Wednesday at The Grove, a country house hotel near Watford.
The meeting is expected to consider new threats, including in the areas of cyber and space, after the alliance last month declared space one of its operational domains alongside air, land, sea and cyber.