Last Updated Apr 25, 2014 10:46 AM EDT
MOSCOW -- Russia's Foreign Minister Sergey Lavrov accused the West on Friday of plotting to seize control Ukraine and said the pro-Russian insurgents in the southeast would lay down their arms only if the Ukrainian government clears out the Maidan protest camp in the capital Kiev.
"The West wants -- and this is how it all began -- to seize control of Ukraine because of their own political ambitions, not in the interests of the Ukrainian people," Lavrov said on Friday.
Ukraine's leader responded by accusing Russia of trying to start "World War Three" by attempting to occupy his nation "militarily and politically."
"The world has not yet forgotten World War Two, but Russia already wants to start World War Three," Prime Minister Arseny Yatsenyuk told lawmakers on Friday in remarks broadcast around the country.
Russia and Ukraine reached an agreement in Geneva last week calling on all parties in the country to lay down arms and vacate public buildings, but neither side moved to abide by the agreement's terms. Pro-Russian militia have been occupying government buildings in more than 10 cities in the eastern Ukraine while the nationalist Right Sector movement is still in control of two public buildings in Kiev.
Pro-Ukrainian demonstrators continue to operate a tent camp on the city's main square, known as the Maidan, and occupy several buildings nearby, including city hall.
Yulia Torhovets, spokeswoman for the Kiev city government, said Ukrainian nationalists have promised to free city hall by the end of this week.
Ukraine authorities, however, say the Kiev occupations are at least tacitly legal because authorities have allowed them.
"Without a doubt, they have all the rights to do this," Viktoriya Syumar, a deputy head of Ukraine's Security and Defense Council, told The Associated Press.
"For seven days, Russia has refused to take a single concrete step in the right direction," U.S. Secretary of State John Kerry said Thursday.
"Not a single Russian official, not one, has publicly gone on television in Ukraine and called on the separatists to support the Geneva agreement, to support the stand-down, to give up their weapons, and get out of the Ukrainian buildings," Kerry said.
Obama warned Thursday in Tokyo that the U.S. had prepared a fresh round of sanctions against Russia as a consequence for Moscow's refusal to condemn the destabilizing violence in eastern Ukraine. But, Mr. Obama said there was still time for Russian President Vladimir Putin to change course and uphold promises to engage with the Ukrainian government.
Speaking Friday in South Korea, Mr. Obama accused Putin of viewing "the world through a Cold War prism," and said the Russian leaders recent decisions, "most clearly with respect to the situation in Ukraine, makes it much more difficult for us to cooperate, and I suspect that's going to linger for some time to come."
The president said Russia's "violations of the sovereignty and territorial integrity of Ukraine is a principle that the United States has to stand up to."
Russia has denied all accusations that it is fueling the unrest in the east of Ukraine -- a denial Kerry mocked in his remarks Thursday.
Lavrov said on Friday the militia in the east "will be ready" to lay down arms and vacate the buildings "only if Kiev authorities get down to implementing the Geneva accords, clear out that shameful Maidan and liberate the buildings that have been illegally seized."
Moscow in March recognized a hastily called referendum in Ukraine's Black Sea peninsula of Crimea and annexed it weeks later, attracting condemnation of the West as well as sanctions targeting individuals. Kerry said that unless Moscow took immediate steps to de-escalate the situation, Washington would impose additional sanctions.
Russia's involvement in Ukraine is already hurting Russia's economy.
The Standard & Poor's credit agency on Friday cut Russia's credit rating for the first time in more than five years. The ratings agency's main concerns the flight of capital and the risk to investment in Russia since the Ukraine crisis blew up late last year.
Credit ratings are important for the economy because they determine the cost of borrowing on international markets. Russian Economic Development Minister Alexei Ulyukayev sought to play down the downgrade, calling it "partly politically motivated."
Elsewhere, there were scattered reports of violence Friday. Ukraine's Defense Ministry said a grenade fired from a launcher caused an explosion in a helicopter at an airfield outside the eastern city of Kramatorsk that injured a pilot.
In southern Ukraine, seven people were injured by a blast at a checkpoint set up by local authorities and pro-Ukraine activists outside the Black Sea port of Odessa. Police spokesman Volodymyr Shablienko said unknown men had thrown a grenade at the checkpoint.Moscow in March took control of Ukraine's Black Sea peninsula of Crimea and annexed it weeks later with the blessing of residents, attracting condemnation of the West as well as sanctions targeting individuals.