The United States said Russia has "days, not weeks" to abide by an international accord aimed at stemming the crisis in Ukraine as Russia in turn accused authorities in Kiev of flagrantly violating the pact and declared their actions would not stand, according to Reuters.
An international agreement to avert wider conflict in Ukraine was faltering on Monday, with pro-Moscow separatist gunmen showing no sign of surrendering government buildings they have seized, Reuters reported.
U.S. and European officials say they will hold Moscow responsible and impose new economic sanctions if the separatists do not clear out of government buildings they have occupied across swathes of eastern Ukraine over the past two weeks, according to Reuters.
Washington, which signed last week's accord along with Moscow, Kiev and the European Union, held open the possibility of slapping further sanctions on a range of Russian officials, Reuters reported.
U.S. Secretary of State John Kerry urged his Russian counterpart Sergei Lavrov on Monday to help implement the Geneva deal, including by "publicly calling on separatists to vacate illegal buildings and checkpoints", spokeswoman Jen Psaki said, according to Reuters.
The United States and the EU have imposed visa bans and asset freezes on some Russians over Moscow's annexation of Crimea from Ukraine last month, Reuters reported.
Washington and Brussels both say they are working on tougher measures they will impose unless Russia's allies in eastern Ukraine back down, although building a consensus is tricky in Europe where many countries rely on Russian energy exports, according to Reuters.
In its account of their telephone conversation, the Russian Foreign Ministry said Lavrov had called on Kerry to "influence Kiev, not let hotheads there provoke a bloody conflict" and to encourage it "to fulfill its obligations unflaggingly," Reuters reported.
U.S. Vice President Joe Biden arrived in Kiev, where he is expected to announce a package of technical assistance, according to Reuters. The visit is likely to be more important as a symbol of support than for any specific promises Biden makes in public.
