The IMF has handed Ukraine a $US17.5 billion ($A22.97 billion) lifeline as the United States agreed to send military aid to bolster its forces against pro-Russian rebels - but stopped short of promising weapons.
The United States also expanded the reach of its economic sanctions, targeting a Russian bank and separatist officials in eastern Ukraine, a move Moscow branded a "political provocation" that would only worsen the crisis.
Ukrainian President Petro Poroshenko welcomed the increased US support in the face of what he called the separatists' "barbaric aggression", despite Washington snubbing growing calls for arms and ammunition.
After a call with US Vice-President Joe Biden and a meeting in Kiev with sympathetic US congressmen, Poroshenko thanked Washington for the offer to send military equipment - but not weapons - worth $US75 million and includes 230 Humvee vehicles and various support, medical and communications gear, officials said.
Ukraine has asked Western powers for weapons to help it fight the rebellion, but the US remains cautious and ally Germany remains opposed to supplying munitions.
White House spokesman Josh Earnest said President Barack Obama was concerned sending more weapons to an already unstable region would lead to greater bloodshed.
Meanwhile, new US sanctions targeted officials in the separatist self-proclaimed Donetsk People's Republic in Ukraine, as well as the Russian National Commercial Bank, the largest bank in Crimea since Russia seized the region from Ukraine last year.
Russia's deputy foreign minister Sergei Ryabkov said Washington's allegations Moscow is backing the separatist movement were "dreary and pointless".
"It's difficult to understand what is guiding the US Treasury Department and other authorities in introducing sanctions and expanding the sanctions lists," he told the Interfax news agency.
The Washington-based International Monetary Fund, meanwhile, gave Kiev breathing room to rebuild its shattered finances, reeling from the fighting in its industrial heartland.
The four-year, $US17.5 billion aid plan replaces an existing IMF program, less than a year old, that proved inadequate to stabilise Ukraine's finances.
The "heavily front-loaded" program will support "deep and wide-ranging policy reforms," IMF managing director Christine Lagarde said.
Ukrainian Prime Minister Arseniy Yatsenyuk said the bailout was a reward for reforms already undertaken. "It obliges us to keep going, not to stop," he said.
Despite a February 12 agreement in Minsk to halt hostilities, fighting has continued around Debaltseve, Donetsk and the port of Mariupol, killing at least 65 Ukrainian troops.
Moscow has withdrawn from the landmark Treaty on Conventional Forces in Europe, and the US has begun to deploy 3000 troops on a three-month exercise to the Baltic region.
In the latest sign Germany too is losing patience, Chancellor Angela Merkel said she would not attend a May 9 World War II commemoration parade in Moscow.
Russia, meanwhile, denies detailed allegations from Kiev and Western capitals it has sent heavy weapons and thousands of troops to support the rebels.
The separatist conflict has killed more than 6000 in 11 months - Ukrainian troops, separatist militiamen, Russian "volunteers" and civilians caught in the crossfire.
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