MOSCOW, October 28 (RIA Novosti) - The Kremlin is satisfied that significant progress has been made in talks with the U.S. on a new strategic arms reduction treaty, a senior aide to the Russian president said on Wednesday.

The current Strategic Arms Reduction Treaty (START-1), the pillar of Russian-US disarmament commitments, expires on December 5.

"The talks are intensive and serious progress has been made. We note the firm determination of both sides to reach a new agreement," Sergei Prikhodko told reporters in Moscow.

He added, though, that several "difficult issues" still remained.

The latest round of talks took place in Geneva two weeks ago. U.S. National Security Adviser James Jones arrived in Moscow on Wednesday to continue negotiations on the new nuclear cuts deal.

The outlines of the new pact were agreed during a meeting between Russian President Dmitry Medvedev and his U.S. counterpart Barack Obama in Moscow in July and include cutting their countries' nuclear arsenals to 1,500-1,675 operational warheads and delivery vehicles to 500-1,000.