David Cameron is to meet the Russian president for face-to-face talks over the Ukraine crisis, Downing Street has said.
The Prime Minister will sit down with Vladimir Putin after the two leaders attend commemorations of the 70th anniversary of the D-Day landings in Normandy on Friday.
"It is an important opportunity to set out the importance of a dialogue between the Russian government and the new Ukrainian government following the presidential elections that have happened over the last week or do in Ukraine," the PM's official spokesman told reporters.
The talks will take place the day after Mr Cameron, US President Barack Obama and other G7 leaders meet in Brussels for a summit at which Russia's annexation of Crimea and the ongoing hostilities in the east of Ukraine will be high on the agenda.
The meeting was hastily arranged after they decided to boycott a planned summit of the G8 - which includes Russia - that Mr Putin was due to host in Sochi this week.
It also comes amid heightened tensions between London and Moscow over reported comments by the Prince of Wales comparing Mr Putin's actions in Ukraine with those of Adolf Hitler.
The spokesman dismissed suggestions that the talks were an attempt to "make peace" with Mr Putin.
"I would underline the real significance of the presidential elections that we have seen in the Ukraine, with a democratically-elected president with a strong mandate - elected in the first round with over 50% of the vote. A clear expression of the will of the Ukrainian people.
"Spelling out, face to face, the importance of the opportunity this offers, and to put it very clearly, face to face, that is the right thing to do."
Mr Cameron is also due to meet Ukraine's newly elected president Petro Poroshenko when world leaders and heads of state gather for the D-Day anniversary - at which the Prince of Wales will represent the Queen.
Mr Poroshenko secured an overwhelming victory in the presidential poll and vowed to rid eastern Ukraine of insurgents and restore calm to the region.
In a telephone call on Friday, the president-elect, a billionaire chocolate tycoon, and the Prime Minister agreed that Kiev must continue to send a "strong message" to Moscow that it has to act to quell the violence.
The Prime Minister's official spokesman said Mr Cameron would "restate our very clear and unchanged position on the Crimea which is we do not recognise the annexation" in his talks with Mr Putin.
He was unable to say whether the meeting was requested by the UK or Russia.
Mr Obama is expected to press European leaders this week to keep up pressure on Moscow over its behaviour towards Ukraine amid fears among some Nato allies such as Poland of a resumption of normal relations.
While there are signs that Russia has begun to move troops away from the Ukrainian border, it still faces criticism for doing too little to ease tensions in the east of the country where deadly clashes continue between pro-Russia separatists and government forces.
Around 100 armed insurgents were reported to have attacked a border guards' camp in Luhansk in the latest clashes.
Mr Putin set up a potentially awkward coming together with Charles in Normandy after he said the heir to the throne's criticism of his actions in Ukraine was "unacceptable" and "not what monarchs do".
Charles's reported remark came during a tour of the Museum of Immigration in Halifax, Nova Scotia, where he and the Duchess of Cornwall paid tribute to Second World War veterans and their families.
Jewish museum volunteer Marienne Ferguson, 78, told the Prince how she and her family fled the Nazis during the war, and said that he responded, "Putin is doing just about the same as Hitler", drawing an apparent parallel with Russia's annexation of the Ukrainian peninsula of Crimea in March.