US Secretary of State John Kerry and his Russian counterpart have agreed on the need to resolve the security situation in eastern Ukraine peacefully, officials say.
It comes as pro-Russia activists continue to occupy state buildings in eastern cities of Ukraine.
The government in Kiev has warned them to enter into dialogue to resolve the crisis or face "force".
The EU, Russia, US and Ukraine are to meet next week for talks on the crisis.
It will be the first four-way meeting since Russia annexed the southern Ukrainian peninsula of Crimea in February. Russian troops are now massed along the borders of the two countries.
Senior US diplomat Victoria Nuland said on Wednesday that expectations were not high for the talks, though it was important to keep the "diplomatic door open".
'Dialogue, not force'
Pro-Russia activists have blockaded state buildings in the cities of Kharkiv, Donetsk and Luhansk since Sunday, calling for greater regional autonomy and condemning the Kiev government.
On Wednesday, Mr Kerry and Russian Foreign Minister Sergei Lavrov "discussed the importance of resolving the security situation in key cities in eastern Ukraine peacefully and through dialogue and they both rejected the use of force to obtain political objectives," says US State Department spokeswoman Jen Psaki.
Mr Kerry and Mr Lavrov spoke twice by phone on Wednesday about the rise in tensions in eastern Ukraine.
In an earlier conversation with the US secretary of state, Mr Lavrov said next week's talks should focus on "dialogue among Ukrainians" and not on bilateral relations among the participants.
Mr Lavrov is expected to meet Mr Kerry, EU foreign policy chief Catherine Ashton and Ukraine's Foreign Minister Andriy Deshchytsia.
Kiev and its allies accuse Moscow of fomenting unrest in the mainly Russian-speaking east of the country as a pretext to possibly seizing more territory - a claim strongly dismissed by Russia.
"These incidents bear all the hallmarks of an orchestrated campaign of incitement, separatism and sabotage of the Ukrainian state, aided and abetted by the Russian security services," Ms Nuland said, echoing earlier comments by John Kerry that Russian special forces had been a "catalyst" behind the unrest.
Ukrainian Interior Minister Arsen Avakov said on Wednesday that an "anti-terrorist operation" was under way in the three regions and would be concluded within 48 hours.
But Moscow has warned Ukraine that using force to end the protests could lead to civil war.
In other developments:
- 56 members of Ukraine's security services held inside the Luhansk offices were allowed to leave following negotiations with local politicians on Wednesday
- Russian President Vladimir Putin suggested state-controlled energy company Gazprom should make Ukraine pay up front for its gas, but said there should be "additional consultations" first
Russia has so far refused to recognise the new authorities in Kiev following the ousting of pro-Russian President Viktor Yanukovych in February.