Russia launched new military exercises near its border with Ukraine on Thursday, showing no sign of backing down on plans to annex its neighbour's Crimea region despite a stronger than expected drive for sanctions from the EU and United States.
In an unusually robust and emotional speech, German Chancellor Angela Merkel warned of "catastrophe" unless Russia changes course, while a man was killed in Ukraine in fighting between rival protesters in a mainly Russian-speaking city.
At the U.N. Security Council, the United States circulated a draft resolution that would declare illegal Sunday's planned referendum on independence for Ukraine's Crimea region.
But Russia, one of the Security Council's five veto-wielding permanent members, made clear it opposed the draft.
"Russia announced they will kill it," a senior Western diplomat told Reuters.
In Berlin, Merkel removed any suspicion she might try to avoid a confrontation with Russian President Vladimir Putin.
"We would not only see it, also as neighbors of Russia, as a threat. And it would not only change the European Union's relationship with Russia," she told parliament. "No, this would also cause massive damage to Russia, economically and politically."
Secretary of State John Kerry said serious steps would be imposed on Monday by the United States and Europe if the referendum on Crimea joining Russia takes place on Sunday as planned.
Merkel, a fluent Russian speaker who grew up in communist East Germany, has emerged in recent days as a leading figure in threatening tough measures against Moscow.
Her foreign minister, Frank-Walter Steinmeier, said that over the weekend, European states would draw up a list of Russians who will face visa restrictions and asset freezes.
Putin declared Russia's right to invade its neighbor on March 1, as Russian troops were already seizing control of Crimea, a Black Sea peninsula with a narrow ethnic Russian majority and a Russian naval base.
Events have moved rapidly, perhaps signalling an effort by Moscow to turn the annexation into a fait accompli before the West can coordinate a response.
In the Ukrainian city of Donetsk, a young man was stabbed to death and more than a dozen people were in hospital after pro-Russian and pro-European demonstrators clashed. The violence was the worst since last month's overthrow of the Moscow-backed president, Viktor Yanukovich.
But in an apparently conciliatory move, Russia backed deployment of an OSCE monitoring mission in Ukraine, including Crimea, the Swiss chairman of the European rights watchdog said.
The leader of pro-Moscow separatist politicians in Crimea, who took power there after armed men seized the regional parliament on Feb. 27, predicted a strong vote in favor of union with Russia in Sunday's referendum.
"We have a survey by renowned Ukrainian and Crimean polling experts showing clearly and plainly that more than 80 percent of people in Crimea are ready to join the Russian Federation," Crimean Prime Minister Sergei Aksyonov told Reuters.
Aksyonov, whose election in a closed session of the regional parliament is not recognized by Kiev, dismissed opponents' accusations he will fix the referendum on Moscow's orders. "We guarantee that all aspects of European law will be followed, including security for voters," he said in an interview.
Western countries dismiss the vote as illegal. "The referendum on Sunday will have no legitimacy, no legal effect, it can have no moral effect. It is a piece of political theater that is being perpetrated at the barrel of a gun," Daniel Baer, the U.S. ambassador to the OSCE, told reporters in Vienna.
At the United Nations, U.S. Ambassador Samantha Power said time was running out for a peaceful solution. She urged Russia to listen to the "remarkably unified" voices of its 14 fellow members of the Security Council and the Ukrainian people.
Diplomats said the one-page resolution would urge countries not to recognize the results of the vote in Crimea. A vote on the draft was postponed until Saturday at the latest to allow time for more negotiations.
Russia has taken territory from its former Soviet neighbors in the past with no serious consequences — in 2008 it invaded Georgia and seized two breakaway regions. But if Putin was hoping for a similarly tepid response this time, he may have misjudged.
In particular, he seems to have alienated Merkel, the Western leader with whom Putin, a German speaker who was once a KGB spy in East Germany, has had the closest relationship.
Merkel was initially more cautious than other Western leaders on the Crimean crisis, but in recent days she has pushed the European Union to match U.S. sanctions. EU action is critical because Europe does 10 times as much trade with Russia as the United States, buying most of its gas and oil exports.
The prospect that EU measures could be implemented as soon as Monday has weighed down the Russian economy.
Goldman Sachs revised its prediction for Russian economic growth this year down to 1 percent from 3 percent, blaming the tension over Ukraine for capital flight that would cripple investment. It said $45 billion had already left Russia this year, mostly Russians stashing money abroad.
The Russian stock market hit a 4-1/2-year low on Thursday and is down 20 percent since mid-February. The cost of insuring Moscow's debt against default rose to its highest level in nearly two years.
The crisis has already forced several Russian firms to put plans on hold for public offerings to raise cash abroad.
Yet none of that appears to have slowed down Putin, who told officials of the Winter Paralympic Games he is hosting in Sochi that Russia was "not the initiator" of the crisis.
The Russian Defense Ministry said 8,500 troops were taking part in new military exercises near the Ukrainian border, testing artillery and rocket launchers.
It was the second big exercise Moscow has ordered since the crisis began; the first, involving 150,000 troops, started a few days before Russian forces seized Crimea.
In a gesture of support for NATO's eastern members, U.S. F-16 fighter jets landed at Poland's Lask air base on Thursday.
Among efforts by the West to isolate Russia politically, the Organization for Economic Cooperation and Development, a 34-member rich nations' club, announced it was suspending membership talks with Russia, under way since 2007.
Moscow has pledged to respond in kind to any Western sanctions. The prime minister of Lithuania, a former Soviet republic that is now an EU member state, said Russia had suspended food product imports through its port of Klaipeda.
But European leaders appear to be calculating that the damage to Russia would be far worse than to Europe. EU-Russian trade makes up 15 percent of Russia's economy and just 1 percent of Europe's. Although EU countries depend on Russian gas imports, storage tanks are full after a mild winter.
Diplomatic lines have been open between Russia and the West throughout the crisis: Kerry and Russian Foreign Minister Sergei Lavrov spoke on Thursday, as they have nearly every day. They are due to meet in London on Friday.
Russia's top general discussed Ukraine with the chairman of NATO's Military Committee by telephone on Thursday, the Interfax news agency said.
The crisis over Crimea began after Yanukovich fled Kiev and pro-European politicians took charge, following three months of demonstrations.
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