WASHINGTON (AFP) - US Secretary of State John Kerry warned Tuesday that Russia was sending agents into eastern Ukraine to "create chaos" the Kremlin could use as a pretext for more military intervention.
With tensions again on the boil in Ukraine, Mr Kerry said he would meet next week with Russian Foreign Minister Sergei Lavrov as Washington seeks to tamp down the most serious East-West crisis since the Cold War.
But Mr Kerry bluntly accused Russia of mounting an "illegal, illegitimate effort to destabilize a sovereign state."
In recent days pro-Kremlin activists have seized government buildings in several cities in Ukraine's east, declaring independence and vowing to vote on splitting from Ukraine.
"Everything that we've seen in the last 48 hours, from Russian provocateurs and agents operating in eastern Ukraine, tells us that they've been sent there determined to create chaos," Mr Kerry told US lawmakers.
And he said Moscow was seeking to further destabilise neighboring Ukraine by fomenting separatism.
"Russia's clear and unmistakable involvement in destabilising and engaging in separatist activities in the eastern Ukraine is more than deeply disturbing," he told the Senate Foreign Relations Committee, a panel he chaired before becoming America's top diplomat.
"No one is fooled by what could potentially be a contrived pretext for military intervention just as we saw in Crimea."
Washington wants to see four-way talks between the United States, Russia, Ukraine and the European Union within the next 10 days to find a way to calm the crisis.
Moscow said on Tuesday it was ready to take part in talks with Brussels and Washington over the future of Ukraine but insisted the ex-Soviet country's Russian-speaking east and south be represented in the negotiations.
Mr Lavrov told reporters that Russia wanted Ukraine's south and east being represented in such discussions.
Russian President Vladimir Putin helped trigger an international crisis last month when his troops invaded Ukraine's Crimean peninsula, a majority Russian-speaking region. Moscow then annexed the region, a move rejected by western nations.
US President Barack Obama announced sanctions on Russian officials and a bank for Moscow's actions in Ukraine.
But some lawmakers like Senate Republican Bob Corker have called for tougher sanctions, saying the White House should impose broader penalties on Russian banks and economic sectors.
"I hope that you will address when we will implement the executive order relative to sectoral sanctions," Mr Corker said, "and hopefully that will be this week if they continue to have the buildup that they have."