Russian President Dmitry Medvedev and his U.S. counterpart Barack Obama have agreed to step up work in order to reach a nuclear arsenal cut deal by December, said the Kremlin press service on Tuesday.

The two heads of state reaffirmed their commitment to achieve a new strategic arms reduction treaty in a telephone conversation initiated by the Russian side on Tuesday, the RIA Novosti news agency reported.

They agreed to give further guidance to enhance the work of experts in order to arrive at meaningful solutions by December.

They "exchanged views on the implementation of the outcome of the Moscow summit, in particular the need for an early start of the practical work of Russian-American Presidential Commission," said a statement posted on the Kremlin website.

They also reiterated the necessity to maintain a trusting relationship between the two presidents and their teams.

The two presidents also raised some pressing international issues, in particular, "an exchange of views on the lessons of the Georgian crisis a year ago, the situation in the Middle East and around Iran."

Tensions in the border area between Georgia and its breakaway region of South Ossetia were heightened days before the first anniversary of Georgia's brief war with Russia in August last year.

Russia has put its troops and border guards deployed in South Ossetia on increased alert following provocations from Georgia, said the Russian Foreign Ministry on Tuesday.

Earlier on Tuesday Medvedev has sent a congratulatory message to Obama, on his first birthday since taking office.

"I believe that the results of the Moscow meeting make it possible to speak of prospects for constructive cooperation between Russia and the United States on the basis of the principles of mutual respect and of each other's interests being taken into account," the Interfax news agency reported citing the message.

Medvedev and Obama signed a framework document on further reductions and limitations of strategic offensive arms during the Moscow summit in early July.

The document stated that each country plans to cut nuclear warheads to 1,500 to 1,675 "within seven years to come."

Strategic arms reduction treaty (START I), signed in 1991 and due to expire in December, places a limit of 6,000 strategic or long-range nuclear warheads on each side and allows the inspection of weapons.

A subsequent Moscow treaty signed in 2002 called for reducing nuclear warheads to between 1,700 and 2,200 by the end of 2012, but made no provision for verification.

A planned American missile defense system in Europe is widely regarded as an obstacle to a new START deal between the U.S. and Russia.

Washington said the planned shield was targeted against "rogue states" like Iran rather than Russia, while Moscow views the proposal as a major threat to its national security.

(Xinhua News Agency August 5, 2009)