Foreign intervention in Ukraine was not among the options discussed by the European Union after all-night talks in Brussels yesterday .
This was revealed as Ukraine's president claimed he had reached a deal with the opposition to end the crisis, following negotiations mediated by three EU foreign ministers.
Europe Minister David Lidington told BBC Radio 4's Today programme: "I don't think anybody is talking about external intervention from sources."
But Mr Lidington expressed reservations about claims that a truce and long-term solution had been agreed.
"There clearly are proposals on the table," he said.
"Those have not yet been agreed by parties, nor is it clear whether there is the political will to move on from a potential joint declaration today to actually follow it up and see changes carried through into practice over a period of time."
His warnings come after the EU agreed to impose sanctions on Ukraine, after security forces were blamed for sniper fire which killed dozens of anti-government protesters on the streets of the country's capital, Kiev.
Sanctions will be applied to Ukraine officials held responsible for the violence, including a travel ban and asset freeze on close allies of president Viktor Yanukovych.
As bloody clashes continued, Prime Minister David Cameron embarked on a round of telephone diplomacy, speaking to world leaders including Russian president Vladimir Putin, who has been the strongest international backer of the Yanukovych regime.
Unconfirmed reports from local medics suggested that at least 70 died and as many as 500 more were injured as marksmen picked off demonstrators after firebombs were thrown at riot police.
Mr Lidington described Mr Cameron's conversation with the Russian president as "cordial".
He said the UK made clear "our concern about the slaughter that was going on in Kiev and the need for a swift, peaceful resolution to that immediate crisis to be found, leading to an inclusive political process within Ukraine".
He said: "We certainly hope that Russia too will use her influence to bring about a permanent cessation of violence and political progress in Ukraine."