US president Barack Obama said the strong international condemnation of Russia's deployment of troops on the streets of Crimea showed the degree to which "Russia is on the wrong side of history".
Speaking ahead of a meeting with Israeli prime minister Binyamin Netanyahu in Washington, Mr Obama urged Russian president Vladimir Putin to use international monitors to protect Russian nationals and speakers within Ukraine if this was Moscow's primary concern.
International law
Mr Obama said the world was "largely united" in believing Russia had violated Ukraine's sovereign and territorial integrity, and breached international law by mobilising troops after Ukraine's pro-Russian president was forced from power following a popular revolt.
He wanted the Ukrainians to be able to determine “their own destiny”, he said.
“What cannot be done is for Russia with impunity to put its soldiers on the ground and violate the basic principles that are recognised around the world,” he said. Describing Russia’s actions in Crimea as “deeply troubling,” he called for a de-escalation of the crisis and urged Mr Putin to turn to international mediation on Ukraine, warning there were “two paths Russia could take” and that over time this would be “a costly proposition for Russia”.
“Now is the time for them to consider whether they can serve their interests in a way that resorts to diplomacy as opposed to force,” said the president. The US was “strongly supportive” of Ukraine’s interim government.
Mr Obama said secretary of state John Kerry would travel to Kiev today to offer a "very specific and concrete package of economic aid".
The US is looking at economic and diplomatic steps to “isolate” Russia and have a negative effect on the country’s economic and status in the world if it continues on this path, Mr Obama said.
The state department said the US was “likely” to introduce sanctions against Russia over the troop deployment in Crimea, a Russian-speaking area of Ukraine.
Weakened by perceived policy climbdowns over Syria and Iran, the president has been pressed by US lawmakers to react more assertively against Russia by restoring the missile defence shield in eastern Europe, cancelling next June's G8 meeting in Sochi or expelling Russia from the group.
A state department spokeswoman said reports that Russia's military had issued an ultimatum to Ukrainian forces in Crimea to surrender or face an assault – denied by Moscow – would, if true, mark a "dangerous escalation for which we would hold Russia directly responsible".
'Considering sanctions'
"At this point, we're not just considering sanctions; given the actions Russia has taken it is likely that we will put those in place, and we are preparing that right now," said the spokeswoman.
Russia could take an alternative path by engaging directly with Ukraine, withdrawing troops back to bases and refrain from interference elsewhere, she said.
Before Mr Obama's comments, US vice-president Joe Biden urged Russian prime minister Dmitriy Medvedev in a telephone call to pull back forces, support the immediate deployment of international monitors and begin a meaningful political dialogue with the Ukrainian government.
