The White House on Monday said President Barack Obama pushed Russian President Vladimir Putin to find a diplomatic resolution to the Ukraine crisis but said "Russia's actions are neither consistent with or conducive to that," according to a Reuters report.
"The president expressed grave concern about Russian government support for the actions of armed, pro-Russian separatists who threaten to undermine and destabilize the government of Ukraine," the White House said in a statement.
"The president noted Russia's growing political and economic isolation as a result of its actions in Ukraine and made clear that the costs Russia already has incurred will increase if those actions persist," it added.
In a statement following Monday's conversation the Kremlin said that the Russian leader rejected the claims of Russian agents' involvement in protests as "speculations based on unreliable information."
Putin said the protests vented public anger about the Ukrainian government's reluctance to recognize the interests of Russian speakers in the east.
More than a dozen government offices and police stations have been seized by mobs. The Ukrainian government and the West have accused Russia of staging the protests.
The Ukrainian authorities have pledged to dislodge protesters. The Kremlin said Putin urged Obama to use American influence in Ukraine to prevent the use of force and bloodshed.