US President Barack Obama and Russian President Vladimir Putin clashed over pro-Russian separatists in Ukraine, in a tense phone call Monday as tensions between Moscow and Washington soared, AFP reports.
A White House statement said the telephone call came at Russia's request and that Obama accused Moscow of supporting "armed pro-Russian separatists who threaten to undermine and destabilize the government of Ukraine."
Senior US officials worry that the separatists, who have seized government buildings, are using a playbook familiar from the run-up to the Russian annexation of Crimea.
A Kremlin account of the call said that Putin told the president that US charges of meddling eastern Ukraine were "unfounded."
Obama told Putin that all "irregular forces in the country need to lay down their arms."
He urged Putin to "use his influence with these armed, pro- Russian groups to convince them to depart the buildings they have seized," the White House statement said.
The White House also took the rare step of confirming that Brennan had flown into Kiev over the weekend.
Russian Foreign Minister Sergei Lavrov had demanded an explanation over Brennan's visit.
Russia's Interfax news agency quoted an unidentified source as saying Brennan recommended Kiev use force against pro-Russian militants in eastern districts.
But White House spokesman Jay Carney blasted claims that Brennan's travel was anything but routine -- and said he was revealing it to rebut "false claims" made by Russia.