LEADERS of the G7 have kept up their rhetoric against Russia, and are threatening to impose further sanctions unless the Russian President, Vladimir Putin, takes action to bring stability to Ukraine.

In a communiqué, the leaders of Canada, France, Germany, Italy, Japan, the United States, and the UK, along with the presidents of the European Commission and EU Council, speak of the "unacceptable interference in Ukraine's sovereign affairs by the Russian Federation", and call on the "illegal armed groups to disarm."

"We are united in condemning the Russian Federation's continuing violation of the sovereignty and territorial integrity of Ukraine," they say. "Russia's illegal annexation of Crimea, and actions to destabilise eastern Ukraine are unacceptable and must stop. These actions violate fundamental principles of international law, and should be a concern for all nations."

In the communiqué the leaders called for the complete withdrawal of Russian military forces from the border with Ukraine, and urged Russia to "stop the flow of weapons and militants across the border". Russia should "exercise its influence among armed separatists to lay down their weapons and renounce violence".

They warn that: "We stand ready to intensify targeted sanctions and to implement significant additional restrictive measures to impose further costs on Russia, should events so require."

But the communiqué also had a positive tone, welcoming last month's election of the new Ukrainian President, Petro Poroshenko, who is due to be sworn in tomorrow.

Mr Poroshenko is expected to meet President Putin at Normandy today, during celebrations marking the 70th anniversary of the D-Day landings, although there are no formal plans for the two men to speak.

The decision to invite President Putin to the commemorations has caused controversy. Simon Heffer, writing in the Daily Mail, typified the criticisms when he said: "Russia may have been our ally in 1944, but its troops were not in this particular theatre of war, and to have Putin there at a time when he is violating all the values for which those heroes fought and died is simply disgusting."

But the French President, François Hollande, defended his decision to invite the Russian leader, saying that he had consulted Western allies before doing so. "We know what we owe to the Russian people - or, more precisely, to the Soviet people - at that time," he said. "This is why President Putin needed to be present. . . The victory against the Nazi barbarism has been possible thanks to the landing, thanks to the will of the Allied countries, and by the Russian people."

The decision was supported by the US President, Barack Obama, who said: "It is entirely appropriate that he is there to commemorate D-Day, given the extraordinary sacrifices that were given by the people of the Soviet Union in World War Two."

President Obama made his comments at a joint press conference with his "great friend and partner" David Cameron.

President Putin, he said, had the "chance to get back into the lane of international law", and the inauguration of President-Elect Poroshenko was an "opportunity" that "Russia needs to seize".

He went on: "Like many Ukrainians, [Poroshenko] wants to forge closer ties with Europe and the United States, but he also recognises that Ukraine will benefit from a constructive relationship with Russia."

Mr Cameron echoed the message, saying: "From the outset of this crisis, the G7 leaders have been united, clear in our support for the Ukrainian people and their right to choose their own future; and firm in our message to President Putin that Russia's actions are completely unacceptable and totally at odds with the values of this group of democracies.

"That is why Russia no longer has a seat at the table here with us."

The President of the European Council, Herman Van Rompuy, has confirmed that, after the election of Mr Poroshenko, the EU will sign the remaining chapters of a security and association agreement with Ukraine by the end of this month.

The political chapters of the agreement were signed on 21 March (News, 21 March). Similar agreements with Georgia and Moldova will be signed on 27 June, in the presence of all 28 EU heads of state or government.

Last night, the leaders of the G7 travelled to Paris for a series of bilateral meetings with other world leaders ahead of today's commemorative events in Normandy.

"David and I agree that whenever our two nations stand together, it can lead a world that is more secure, more prosperous, and more just; and we will be reminded of that . . . in Normandy, when we mark the 70thanniversary of D-Day," President Obama said.

"On that day, as on so many others, American and British troops stood together and fought valiantly alongside our allies.

"They didn't just help to end the war, they helped to turn the tide of human history, and are the reason we can stand here today in a free Europe and with the freedoms our nations enjoy. Theirs is the legacy that our two nations and our great alliance continue to uphold."

Mr Cameron said: "As we stand together in Europe on the 70th anniversary of the D-Day landings, we should remind the world of the strength and steadfastness of the bond between the United Kingdom and the United States. Seventy years ago . . . our countries stood like two rocks of freedom and democracy in the face of Nazi tyranny.

"Seventy years ago . . . thousands of British and American soldiers, with their Canadian and Free French counterparts, were preparing to cross the Channel in the greatest liberation force that the world has ever known.

"Those young men were united in purpose to restore democracy and freedom to continental Europe - to free, by force of arms, ancient European nations, and to allow the nations and peoples of Europe to chart their destinies in the world.

"Thousands of those young men paid the ultimate price, and we honour their memory."