US President Barack Obama says Russia is not "fooling anybody" over the crisis in Ukraine after Vladimir Putin denied Russian forces were operating on the flashpoint Black Sea peninsula of Crimea.
In a show of support for the new interim leaders in Kiev, visiting US Secretary of State John Kerry condemned Russia's "act of aggression" and accused Moscow of "working hard to create a pretext for being able to invade further".
Pro-Kremlin forces are in de facto control of the strategic, majority-Russian Crimean peninsula where Ukrainian troops remain blocked inside their barracks in the most serious stand-off between the West and Russia since the end of the Cold War.
Amid the tensions, Russia carried out a successful test launch of an "advanced" intercontinental ballistic missile, state news agencies reported. The US was informed of the test earlier this week, a US defence official said.
World financial markets meanwhile rebounded on Tuesday as traders interpreted comments by Putin that force was "a last resort" as a sign that the situation in the nation of 46 million people was easing.
Ukraine's interim Prime Minister Arseniy Yatsenyuk also announced his government had made the first "timid" contacts with Russian leaders aimed at resolving the crisis.
But the rhetoric from the United States and Russia remained tough.
Obama said the European Union and allies like Canada and Japan all believed Russia had violated international law by mobilising troops following the February 22 ouster of pro-Kremlin president Viktor Yanukovych.
"President Putin seems to have a different set of lawyers, maybe a different set of interpretations. But I do not think that is fooling anybody," Obama said during a visit to a school in the US capital.
Putin, breaking more than a week of silence with a media conference in Moscow, said his country reserved the right to use "all available means" to protect Russians in Ukraine. "This is a last resort," he added.
Responding to claims by Ukraine's new authorities that thousands of Russian troops had poured into Crimea in recent days, Putin said that only "local forces of self-defence" were surrounding Ukrainian military bases in the region.
Asked if Russian forces took part in operations in Crimea, he said, "No, they did not participate", adding: "There are lots of uniforms that look similar."
When told of Putin's remarks by a reporter in Kiev, Kerry responded: "He really denied there were Russian forces in Crimea?" and shook his head, bewildered.
The top US diplomat also laid flowers and lit a candle at the scene of memorials to the nearly 100 people who died in clashes on Kiev's Independence Square last month.
The square was the focal point of three months of protests sparked by Yanukovych's decision to reject a key EU deal in favour of closer ties with Moscow.
In a further public boost to Ukraine's new Western-backed authorities, the US confirmed $US1 billion in loan guarantees to help shore up Ukraine's debt-laden economy.
The European Commission also offered an aid package reportedly worth more than one billion euros, as cash-strapped Ukraine says it needs 25 billion euros ($A38.68 billion) over two years.
Share
