The upcoming G8 summit looks likely to be shelved, according to David Cameron, following a ramping up of international tensions over pro-Russian forces taking control of the region of Crimea. The group of nations is scheduled to meet in Sochi in June, however the prime minister said it was "hard to see" how the gathering could go ahead.
During Prime Minister's Questions on Wednesday, Cameron said: "What I think we need to do is first of all be absolutely clear that the status quo we are faced with today, where Russian troops are outside their bases in the Crimea, is unacceptable.
"As I have said, costs and consequences need to follow from that. That is why, for instance, we have suspended preparations for the G8 meeting. Indeed, it is hard to see in these circumstances how a G8 meeting can properly go ahead."
The PM added: "When we look at the diplomatic, economic and political steps we can take, nothing should be off the table. There has been some progress in putting together a contact group ... to start having a group of countries around Russia and Ukraine to encourage such dialogue to take place. That is the single most important thing that could happen to de-escalate the situation.”
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Russia declined to attend a meeting convened under the 1994 Budapest Memorandum on Wednesday morning, which provided Ukraine with assurances of security and territorial integrity when it gave up its nuclear weapons. But Russian foreign secretary Sergey Lavrov will be at talks in the French capital that had been scheduled to discuss support for Lebanon, and are now expected to be dominated by the situation in Ukraine.
British Foreign Secretary William Hague told reporters: "I am not optimistic about the outcome of that but of course it is right to try every diplomatic opportunity to de-escalate the crisis. If we cannot make progress on that, of course there will be costs and consequences... there has to be for such a violation of the independence and sovereignty of another nation.
"It will be a test this afternoon of whether Russia is prepared to sit down with Ukraine." Hague appeared to play down the prospects of significant EU action being agreed, saying reaching a unified position required "a lot of hard work".
While insisting Britain was "closely aligned" with France, he did not make the same claim about Germany, which has the strongest trading links with Russia. "It is true that bringing together 28 nations in agreement on foreign policy-specific decisions always requires a lot of hard work," Hague said.
"Some of the most important consequences could very well be in the long term. Here we have seen Russia do in the Crimea what has happened in Georgia some years ago, what has happened in Moldova, and it becomes a long-term pattern of behaviour that I think will change the relationship between European nations and Russia."
The UK and US have urged Moscow to order troops which have seized key military and administrative locations in the Crimea back to their barracks and to allow the deployment of international observers from the Organisation of Security and Co-operation in Europe to the southern peninsula, which is part of Ukraine but is home to Russia's Black Sea fleet, under an agreement signed in 1997.
But speaking in Madrid en route to Paris, Lavrov repeated president Vladimir Putin's denial that the soldiers operating in uniforms without insignia were Russian troops, or under Moscow's control. Troops of the Black Sea fleet had stepped up security around Russian military facilities in Crimea but had not deployed outside their bases, he said.
The decision on whether monitors should be admitted was not for the Kremlin, but for the "supreme Soviet" of Crimea as well as the government in Kiev, which Lavrov said was not in control of the largely Russian-speaking peninsula.
"It is clear that those who sit in the Ukraine parliament do not control the entire territory of the country - in the Crimea, for instance, and in other areas where people do not want to recognise the legitimacy of those who came to power in an unconstitutional way," said Lavrov.
"You should be talking to the people who control the situation in the Crimea, to their supreme Soviet. If they would want to invite international monitors and if the government in Kiev would do the same, that would be the decision of Ukraine."
Lavrov said he would tell his Western counterparts that the "unbreachable foundation" for a resolution to the crisis should be the implementation of the February 21 agreement reached between Yanukovych and protesters and signed by France, Germany and Poland in the presence of a Russian mediator, which provided for a return to Ukraine's old constitution and presidential elections by the end of the year.
Within hours of the deal, Yanukovych had left Kiev and his regime crumbled as protesters stormed government buildings. The way out is possible on the basis of the agreement of February 21," said Mr Lavrov. "What has been agreed should be implemented."