Russia's Prime Minister Vladimir Putin (C) congratulates journalists from the government pool group with the upcoming New Year holiday in Moscow, December 29, 2010. [Agencies]

MOSCOW - Russian Prime Minister Vladimir Putin praised the New START nuclear arms treaty with the United States on Wednesday in his first remarks on the pact since the US Senate approved it last week.

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Putin lauded President Dmitry Medvedev for forging the treaty with President Barack Obama - a clear signal of approval for the agreement from Russia's paramount leader, who also stands to benefit from the improvement in bilateral ties.

He told reporters the pact was an "unconditional success for President Medvedev in foreign policy".

Analysts say Russia would not have agreed the treaty without Putin's support and that the Kremlin-controlled parliament is all but certain to ratify it after the holidays.

It is the main product of Obama's effort to "reset" long-strained ties between Washington and Moscow, a drive that Medvedev has embraced enthusiastically.

Putin, whose focus as prime minister is on domestic issues, has rarely commented on the New START treaty and at one point during year-long negotiations made remarks that cast doubt on the chances for agreement.

On Wednesday, Putin suggested the treaty would bolster international security but also help Russia develop its economy by improving the investment climate.

"I would like to congratulate Dmitry Anatolyevich (Medvedev) on the completion of work on the START treaty," Putin said at a government meeting attended by the president.

"This is a serious decision which will have an impact not only on issues related to international security," Putin said.

"For us it is important because it creates favourable external conditions for realisation of social and economic initiatives inside this country."

Signed by Medvedev and Obama in April, the pact commits the United States and Russia to reducing their arsenals of deployed strategic nuclear weapons and establishes monitoring rules officials say will improve trust between the Cold War foes.

Putin steered Medvedev into the presidency as his chosen sucessor in 2008 and has hinted he will either return to the Kremlin or leave his protege in place in the 2012 election.

Analysts say Medvedev was given a mandate to improve relations with the West, which deteriorated during Putin's presidency and hit a low with Moscow's August 2008 war with pro-Western Georgia, in hopes of strengthening Russia's economy.

At the meeting on Wednesday, Medvedev lamented a lack of progress in attracting investment, saying "there is very little improvement" in the investment climate. "We need to work on it."

Putin said questions remain over Russia's campaign for membership of the World Trade Organisation, which has been helped by Obama's public backing as part of the "reset".

"There is no final result yet but we have agreed the main parameter with our main partners," Putin said.

Russia "can be expected" to join the WTO in 2011, he told reporters, in line with predictions by other officials.

"I cannot even imagine what can disrupt our accession plans. Of course if somebody wants to, some tricks that would stand in the way of our accession can be found," he added, possibly referring to Georgia's suggestion it could block Russian entry if it is unhappy with customs controls on its border with Russia, parts of which lie in Moscow-backed separatist regions.