The United States and Russia were set to hold a second day of talks aimed at replacing a landmark Cold War-era nuclear disarmament treaty that expires in December, officials said.

The talks on a successor to the Strategic Arms Reduction Treaty (START) are a central part of US President Barack Obama''s desire to "reset" strained ties with Russia and their result could have far-reaching implications for global security.

Signed in 1991, START led to deep cuts in the US and Russian atomic arsenals and is seen as a cornerstone of strategic arms control, but the agreement expires in December.

Russian foreign ministry spokesman Igor Lyakin-Frolov said the first day of talks took place Tuesday and would continue Wednesday as planned. He made clear though there would be little public information about them.

"By agreement of both sides the talks will be discreet and they will only release an agreed joint statement at the end," Lyakin-Frolov told AFP.

The two-day negotiating session marks the formal start of the process, though the two sides had several preliminary meetings to help break the ice.

Productive negotiations would boost Obama''s vision of a world free of atomic weapons and help set the stage for a fence-mending summit in July when Obama travels to Moscow to meet Russian President Dmitry Medvedev.