The United States and Russia were set to hold talks Wednesday aimed on easing East-West tension over Ukraine.
Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov will meet face-to-face for the first time since the crisis escalated, after a conference in Paris attended by all five permanent members of the U.N. Security Council.
The West hopes to persuade Moscow to pull its forces back to base in Crimea and avert the risk of a war.
NATO and Russia will hold parallel talks in Brussels amid concerns that a standoff between Russian and Ukrainian soldiers in Crimea could still spark violence, or that Moscow could also intervene in Russian-speaking eastern Ukraine.
French Foreign Minister Laurent Fabius said European Union leaders meeting in Brussels on Thursday could decide on sanctions against Russia if there is no "de-escalation" by then.
President Vladimir Putin on Tuesday defended Russia's actions in Crimea, a strategic Black Sea peninsula that is part of Ukraine but used to be Russian territory, and said he would use force only as a last resort.
This eased market fears of a war over the former Soviet republic. But Russian forces remain in control of the region and Putin gave no sign of pulling servicemen, based in Crimea as part of the Black Sea fleet, back to base.