Armed men who call themselves members of Ukraine's disbanded elite Berkut riot police force stand at a checkpoint on a highway that connects the Black Sea Crimea peninsula to mainland Ukraine near the city of Armyansk, on February 28, 2014 Viktor Drachev/AFP UNITED NATIONS (Reuters) - Ukraine on Saturday asked the United States and other key members of the U.N. Security Council to help safeguard its territorial integrity after Russia announced plans to send armed forces into the country's autonomous Crimea region.

"We can stop the expansion of this aggression," Ukraine's U.N. Ambassador Yuriy Sergeyev told reporters after addressing a closed-door U.N. Security Council meeting on the crisis in his country.

He said that Russia's military aggression had 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 said.

"Still there is a possibility for world leaders to speak with (Russian) President (Vladimir) Putin and prevent ... the further deterioration of the situation," he said.

U.N. spokesman Martin Nesirky said Secretary-General Ban Ki-moon planned to speak with Putin on the telephone.

"The Secretary-General reiterates his call for the full respect for and preservation of the independence, sovereignty and territorial integrity of Ukraine," Nesirky told reporters.

"He calls for an immediate restoration of calm and direct dialogue between all concerned to solve the current crisis," he added.

The 15-nation council's emergency meeting on Ukraine - the second in as many days - was convened at the request of Britain. British Ambassador Mark Lyall Grant told reporters on the way into the meeting that he called for the meeting to learn "what justification Russia claims to have" for its actions in Ukraine.

Diplomats told Reuters that inside the closed-door consultations there was a heated debate on whether to hold a public meeting, as the U.S. and other Western delegations are demanding, or to keep it all behind closed doors, as Russia wants.

The council met on Friday to discuss the crisis in Ukraine's Crimea region but took no formal action, as expected. The meeting highlighted the deep divisions between the United States and other Western nations and Russia, which has a major Black Sea naval base in the Crimea.

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.

Russian Ambassador Vitaly Churkin, however, said any military movements by Russian forces there were in compliance with its agreement with Kiev on maintaining its naval base there.

Russia is a veto-wielding permanent member of the Security Council and, therefore, able to block any actions proposed by its members.

(Reporting by Louis Charbonneau; +1-646-591-5178; editing by Gunna Dickson) nL1N0LY0H7