WHITE HOUSE - Russia says it has prepared proposals to defuse the Ukraine crisis, but Washington says Moscow needs to show evidence that it wants peace.
Russian forces continued to consolidate their presence in the Crimea, on Monday taking control of a military hospital.
Meanwhile, protests - for and against Russia - continued.
In Washington, U.S. officials kept up their push Monday to get Russia to back down and de-escalate the crisis.
“Those troops should go back to their bases," said White House Spokesman Jay Carney. "Russia ought to engage with the Ukrainian government in dialogue with international participation.”
Meanwhile, NATO says it will deploy reconnaissance aircraft to fly over Poland and Romania to monitor events in Ukraine. The U.S. has boosted its presence in Poland with additional aircraft and personnel.
NATO says it is deploying reconnaissance aircraft along the borders of member states Poland and Romania, to monitor the crisis in nearby Ukraine.
The Western military alliance said the decision to send AWACS (Airborne Warning and Control Systems) surveillance planes was made on Monday, with the approval of the 28 members. It said the deployment is designed "to enhance the alliance's situational awareness."
However, the U.S. and its European allies have emphasized they do not want the crisis resolved by force.
Hopes for a diplomatic solution emerged Monday, with Russia's foreign minister saying he has a set of proposals to defuse the crisis.
But Washington says it needs evidence that Russia wants to engage in peace, and that includes opening a dialogue with Ukraine's government - which Moscow does not recognize.
President Obama has invited Ukraine's prime minister to visit the White House in the coming days, in what Carney said is a clear message.
“We're making it clear to the new government of Ukraine that we support them,” he said.
The U.S. has already said the outcome of an upcoming Russian-sponsored referendum on whether Crimea should become part of Russia will be illegitimate, but stopped short of threatening further actions beyond the visa restrictions and financial sanctions it has already announced.