(Recasts, adds U.N. envoys)
By Louis Charbonneau
UNITED NATIONS, March 1 (Reuters) - Russia and Western nations on the U.N. Security Council accused each other of meddling in Ukraine's internal affairs on Saturday as the United States called for the immediate deployment of international monitors to the former Soviet republic.
The hurling of accusations back and forth at the United Nations highlighted the deep gulf between Moscow on one side and the United States and Europe on the other when it comes to countries in what Russia considers its sphere of influence.
Ukraine's U.N. Ambassador Yuriy Sergeyev asked the United States and other key members of the 15-nation council to help safeguard its territorial integrity after Russia announced plans to send armed forces into neighboring Ukraine.
But it was not immediately clear how they could do that given Russia's veto powers on the Security Council.
"The situation continues to deteriorate," Sergeyev told the council, adding that Russian deployments in his country are "an act of aggression against the state of Ukraine ... posing a serious threat to our sovereignty and territorial integrity."
He described the Russian actions as aggression that violated a 1994 agreement on safeguarding Ukraine's territorial integrity and called on the other four permanent U.N. Security Council members to use their diplomatic powers to help his country.
"Now what we are doing is we are addressing for other guarantors (of Ukraine's sovereignty) - the United States, the United Kingdom, France, and China - to perform their guarantees," Sergeyev told reporters.
Russian Ambassador Vitaly Churkin dismissed Sergeyev's criticisms and described the council meeting on the Ukrainian crisis as a "game without rules."
U.S. Ambassador to the United Nations Samantha Power called for the "immediate deployment" to Ukraine of international monitors from the United Nations and the Organization for the Security and Cooperation in Europe (OSCE).
"It is ironic that the Russian Federation regularly goes out of its way in this chamber to emphasize the sanctity of national borders and of sovereignty, but Russian actions in Ukraine are violating the sovereignty of Ukraine and pose a threat to peace and security," Power said.
"It is time for the Russian intervention in Ukraine to end," she said.
Sergeyev voiced clear support for Power's call for international observers, adding that his government wants Russian troops to be "immediately withdrawn."
Churkin accused the United States and European Union nations of interfering in Ukrainian affairs and encouraging the street demonstrations that sparked a recent violent crackdown on the streets of Kiev and eventually led to the ouster of former President Viktor Yanukovich.
Those demonstrations were "encouraged from abroad" and helped spark a crisis that did not have to come about, he said, echoing allegations that Moscow has made repeatedly.
"Why did there have to be these crude interventions in the internal sovereignty of Ukraine?" Churkin said.
British Ambassador Mark Lyall Grant rejected Churkin's criticism of EU countries and called for an end to Russian violations of its neighbor's borders. He also demanded that Russia explain the legal basis for deploying its military forces to Ukraine.
"This action is a grave threat to the sovereignty independence and territorial integrity of Ukraine," he said. "We condemn any act of aggression against Ukraine."
The foreign ministry of temporary council member Lithuania said in a statement that Russia's actions were "a blatant breach by Russia of international law and violation of sovereignty and territorial integrity of Ukraine."
After the public debate, the Security Council continued with its discussions behind closed doors.
When the meeting ended, Luxembourg Ambassador Sylvie Lucas, council president for the month of March, told reporters that members had spoken about the need for "deescalation of the situation" and stressed the importance of respecting unity and territorial integrity of Ukraine.
Secretary-General Ban Ki-moon spoke with Russian President Vladimir Putin on the telephone. "I appealed to President Putin to urgently engage in direct dialogue with the authorities in Kiev," Ban said in a statement about his conversation with the Russian president.
"I am gravely concerned by some of the recent events in particular those that could in any way compromise the unity, sovereignty and territorial integrity of the country," he said.
Sergeyev said Russia, which has a major Black Sea naval base in the Crimea, rejected Kiev's offers of dialogue.
The council met on Friday to discuss the crisis in Ukraine's Crimea region but took no formal action, as expected. Nor did it take any action on Saturday.
At Friday's session, Ukraine accused Russia of illegal military incursions onto Ukrainian territory, while U.S. and European delegations warned Moscow to withdraw any new military forces deployed in neighboring Ukraine.
Churkin, however, said any military movements by Russian forces there were in compliance with its agreement with Kiev on maintaining its naval base there. (Reporting by Louis Charbonneau; Editing by Gunna Dickson and Cynthia Osterman)