A US team may arrive in Russia next month to inspect the country's latest range of nuclear missiles under a new disarmament treaty signed by the two sides this year, the foreign ministry said Thursday.

Secretary of State Hillary Clinton and Russian counterpart Sergei Lavrov exchanged documents formally bringing the new START treaty into force in Munich on February 5.

Besides slashing existing nuclear warhead and missile ceilings, the treaty allows the two sides to inspect each other's nuclear facilities -- seen as a vital confidence-building measure.

Full on-site inspections are allowed within 60 days of the treaty going into effect, and a top Russian diplomat said Thursday they could potentially begin in April.

"The first inspection check may occur two months after the new START treaty's signature," Deputy Foreign Minister Sergei Ryabkov was quoted as saying by Interfax.

"The inspection may not occur before the first two months" are up, he added.

Ryabkov's comments came moments after one of Russia's top nuclear weapons designers said he expected the first US team to arrive this week.

Yury Solomonov, who heads the Moscow Institute of Thermal Technology that is developing the Bulava submarine ballistic missile, said the first inspectors would check on Russia's latest Yars intercontinental ballistic missile.

He said the US side had already inspected Russia's earlier Topol-M missiles under terms of the old START treaty that expired at the end of 2009.

"So it is only natural that the US side would want to see the new missiles, which have not been shown before," Solomonov was quoted as saying by Interfax.

He added that the first US team would stay in Russia until March 22.

The new START reduces previous warhead ceilings by 30 percent and limits each side to 700 deployed long-range missiles and heavy bombers.

The original 1991 pact expired at the end of 2009.