Lavrov, for his part, blamed the West for raising tensions, saying Friday that the pro-Russian militants would only lay down their weapons if the Ukrainian government first clears out its own protesters in the capital.
Underscoring the effect that wider sanctions could have on Russia's economy, credit agency Standard and Poor's cut Russia's credit rating to BBB- . The agency said it is concerned about increased capital outflows from Russia, and said the rating could be cut further if sanctions are tightened.
Washington has accused Moscow of failing to uphold the four-party deal it signed last week calling for all parties in Ukraine to lay down their weapons and vacate public buildings. U.S. Secretary of State John Kerry said Moscow has not taken "a single step" to de-escalate tensions since the deal was signed in Geneva.