Media playback is unsupported on your device Media caption William Hague: "This will turn out, over time, to be quite a big miscalculation"

Russia has made a "big miscalculation" in entering Crimea, UK Foreign Secretary William Hague has warned.

He told the BBC that Western countries could impose "far-reaching" economic sanctions if no diplomatic solution was reached between Russia and Ukraine.

Mr Hague warned Moscow that European policies could be "recast" to reduce Russian leverage over Europe.

PM David Cameron has phoned Russian President Vladimir Putin and urged him to de-escalate the crisis.

Downing Street said President Putin agreed it was in "all our interests to have a stable Ukraine", during the conversation - which also included German Chancellor Angela Merkel - on Sunday morning.

"The prime minister made clear that we, along with our European and American partners, want to work with Russia to find a diplomatic solution to the situation in Ukraine, including Crimea", a spokesman said.

Mr Cameron urged Mr Putin to support the formation of a contact group that could lead to direct talks between the governments of Russia and Ukraine.

In a separate statement, Mrs Merkel said she "regrets" a lack of progress on forming the group.

And the Kremlin said the leaders "exchanged points of view on what the international community could do to normalise" the situation.

Earlier, Douglas Alexander, Labour's shadow foreign secretary, called for a "clear timetable" of possible measures against Russia to be set out.

'Ridiculously quick'

Tensions have continued to rise in Crimea after Russian forces and pro-Moscow gunmen seized control of the Ukrainian autonomous region last month.

Russia denies sending troops to the region, but has said it reserves the right to defend its interests and those of ethnic Russians in Crimea.

Ukraine's new leaders, who came to power after the ousting of elected president Viktor Yanukovych, have vowed not to cede "a single centimetre" of territory to Russia.

Tens of thousands of people in Ukraine have held rival pro-unity and pro-Russian rallies, with some turning violent.

Image copyright Getty Images Image caption Rallies backing the pro-Russian authorities in Crimea have been held in parts of south-eastern Russia, including Rostov-on-Don

Image copyright Reuters Image caption In Sevastopol in Crimea, violence flared at one pro-Ukrainian demonstration when ethnic Russians attacked protesters

Mr Hague told BBC One's Andrew Marr Show he would be speaking to his US counterpart, John Kerry, later on Sunday about the crisis.

It follows a US warning to Russia that any moves to annex Crimea would close the door to diplomacy.

New pro-Russian authorities there have called a 16 March referendum to ask residents whether they want to secede from Ukraine and join Russia.

Our security of supply in gas - people shouldn't be worried about that Ed Davey, Energy Secretary

Mr Hague said this was happening "ridiculously quickly", adding: "The world will not be able to regard that as free or fair."

He also said: "I think it would be wrong to think Russia has won in some sense. I think this will turn out over time to be quite a big miscalculation."

Mr Hague also said European countries could reduce energy supplies from Russia and import more gas from the US.

He ruled out military action against Russia but said there was a danger of a "real shooting conflict" over Crimea.

Russians living in the UK legally would not be affected by any action taken, he said.

Mr Hague insisted "there clearly are Russian troops in Crimea".

"There is no plausible explanation of where else they have come from."

Leverage

The Kremlin "clearly had a well-rehearsed plan to move militarily" into the region, Mr Hague said, but conceded that none of the sanctions being considered by the West could remove Moscow's military forces.

However, he said: "The long-term effect will be to unite Ukraine more against Russian domination of their affairs and to recast European policies in a way that will reduce Russian leverage over Europe.

"There would be far-reaching trade and economic consequences [for Russia]."

Last week, the European Union suspended talks with Moscow on setting up visa-free travel for Russians in Europe.

Mr Hague said: "I think [the Russians] do care about the international reaction to what they've done. The reaction is strong."

He warned of possible visa freezes and travel bans, which would "be taken very seriously by the individuals concerned".

The foreign secretary also said it was important for Nato countries to improve their defence capabilities in light of the situation, warning many Nato countries had "reduced their defence spending to a very low level".

Image copyright Getty Images Image caption Thousands have been taking part in a pro-Russian rally in Simferopol, Crimea

Image copyright Getty Images Image caption People gathered in the north-eastern Ukrainian city of Kharkiv to pray for peace

Asked about the security of EU gas supplies in the event of sanctions against Russia, Mr Hague said: "This is now beginning to be discussed between European politicians, including ourselves, and Americans."

He added: "There is clearly an increased case for American gas exports to Europe."

Mr Hague said he had visited Baku in Azerbaijan in December for the inauguration of a new pipeline "that will now take several years to construct - from the Caspian Sea into southern Europe", bringing gas supplies which do not pass through or come from Russia.

"The case for such developments will increase now," he said.

Energy Secretary Ed Davey told the BBC that the UK had "very secure supplies" of natural gas from the North Sea via pipelines from Norway.

Image copyright Reuters Image caption Mr Hague said troops in Crimea had "clearly" been sent by Russia

But Mr Davey said: "If there was an escalation, if we saw military conflict, if that conflict went on for months and months and months, there could be an impact on prices."

Russia supplies about 1% of the UK's gas but up to a third of the amount reaching some EU countries, including Germany.

For Labour, Mr Alexander said "all economic and diplomatic options should remain on the table".

"It is also vital that the UK, along with EU allies, sets out a clear timetable for taking further economic and financial measures if Russia fails to change course in the days ahead," he said.