By Michelle Nichols

UNITED NATIONS (Reuters) - Russia is prepared to consider ways of making it easier for Libya's government to buy arms, but voiced serious concern about lifting an embargo on the North African state already awash with weapons, Russia's U.N. ambassador said on Monday.

Libya's Prime Minister Ali Zeidan said last week he planned to ask the U.N. Security council to lift the embargo, which was imposed at the start of an uprising in 2011 that culminated in the ouster of dictator Muammar Gaddafi.

Russia's U.N. Ambassador Vitaly Churkin, who is president of the Security Council this month, said there were concerns about the Libyan government's lack of authority in the vast desert country and the spread of weapons its borders.

He said Libya had not yet made an official request for the arms embargo to be lifted, but the issue would likely be discussed by the 15-member council before a meeting on Libya later this month.

"Some council members do have reservations about lifting the arms embargo," Churkin told reporters, noting that Libya's government was already able to purchase weapons with the approval of a Security Council sanctions committee.

"Of course it can be regarded as a somewhat cumbersome procedure even though it's supposed to happen rather quickly," Churkin said. "I think we will also be looking at ways maybe to facilitate the possible acquisition of arms by the Libyan government short of full fledge lifting of the arms embargo."

The Libyan government has struggled to exert authority across the country. State security forces remain weak and militias, made up of former rebel fighters, hold the power on the ground.

Libya's official LANA news agency quoted army chief of staff Yussef al-Mangoush last week as saying Libya was planning to rebuild its army and wanted to sign contracts with international consultancies to help carry this out and assess what kind of equipment it needed in the future.

Libya's south has become a smuggling route for weapons which have reached al Qaeda militants deep in the Sahara desert. The lawless region is also a conduit for trafficking legal and contraband goods.

In the eastern city of Benghazi - the cradle of the revolt against Gaddafi - there has been a wave of violence against diplomats, military and police, including a September 11 attack last year that killed the U.S. ambassador and three other Americans.

"It does give one pause and I think suggests a need to reflect very carefully on the advisability of lifting the arms embargo," Churkin said of the security concerns facing Libya.

Russia is still bristling that its abstention from a U.N. vote in 2011 allowed NATO air strikes to help Libyan rebels trying to topple Gaddafi. Russian officials accused the United States and its allies of overstepping their mandate.

(Reporting by Michelle Nichols; editing by Christopher Wilson)