US President Barack Obama has held a "constructive" phone call with Russian President Vladimir Putin, in pressing for a swift end Ukraine's deadly crackdown on protesters.
The call on Friday came at a prickly time in US-Russia relations with the two sides at odds over Ukraine, Syria and other issues, but also after Obama took pains to reject the idea a new Cold War-style confrontation was brewing.
A senior US official described the call as "constructive" but also warned that the agreement reached in Kiev between the government and top opposition leaders was "very, very fragile".
Putin and Obama agreed the Ukraine deal needs to be swiftly implemented and all sides need to refrain from violence.
"President Putin affirmed that Russia wants to remain part of the implementation process. They also talked about the need to stabilise the Ukrainian economy and to get Ukraine back on a peaceful path," the official said, on condition of anonymity.
The call also touched on other issues including Syria, where Russia backs President Bashar al-Assad, to the fury of the United States, and the Sochi Winter Olympics.
Washington had offered staunch support for protesters in Kiev, demanding political concessions from the Moscow-backed government of President Viktor Yanukovych and had warned of "consequences" if violence, which killed 100 people did not stop.
The White House gave an initial welcome to the deal and praised European Union diplomats who helped to broker it.
