Russia does not rule out reaching initial agreement with the United States on nuclear arms cuts by the time President Barack Obama visits Moscow in July, a Kremlin spokeswoman said on Tuesday.

"A complicated process is under way," said President Dmitry Medvedev's spokeswoman, Natalya Timakova, referring to nuclear arms reduction talks between Russia and the United States.

"I wouldn't say that we won't be able to achieve a more concrete accord," she told journalists in a telephone briefing, adding it was "too early to draw conclusions."

US and Russian officials were meeting in Geneva this week for a second round of negotiations on renewing the Strategic Arms Reduction Treaty (START), a key accord signed in 1991 just before the break-up of the Soviet Union.

Obama is due to visit Moscow on July 6-8 amid high hopes of a "reset" in relations following tensions under George W. Bush and Medvedev's predecessor, Vladimir Putin.