MOSCOW – Russia said on Thursday that talks with the United States on reducing vast arsenals of Cold War nuclear weapons were proceeding constructively ahead of a visit by U.S. President Barack Obama to Moscow in July.

Finding a replacement for the 1991 Strategic Arms Reduction Treaty (START I) before it expires on December 5 would mark a thaw in relations between the world's biggest two nuclear powers.

The two sides are seeking to narrow differences before Obama and Russian President Dmitry Medvedev meet in Moscow on July 6-8. Both countries have already stated their desire to reset relations, which deteriorated to near Cold War levels.

There is an active negotiating process going on at the moment to work out an agreement that would replace the Strategic Arms Reduction Treaty, Russian Foreign Ministry spokesman Andrei Nesterenko told reporters at a weekly briefing.

The negotiations are taking place in a constructive and business-like manner. We count on the presidents being able to make an announcement on interim results at the July summit, he said.

The next round of U.S.-Russia negotiations on START will take place June 23-24 in Geneva, he said. Two rounds of talks have already taken place.

Obama and Medvedev have said the new arms deal should cut stockpiles below those in the 2002 Strategic Offensive Reductions Treaty (SORT), under which both sides are to cut their arsenals to between 1,700 and 2,200 warheads by 2012.

Russia also wants to link the nuclear talks to U.S. plans to deploy an anti-missile shield in Europe and has pushed for the United States to put a limit on the number of delivery systems -- the rockets or other means that deliver weapons.

Nesterenko said the Summit agenda would concentrate on improving practical cooperation, for example on countering nuclear proliferation but would also discuss August's Afghan elections and broader political and economic ties.

There is intensive preparation... and we hope for a highly productive Moscow summit, Nesterenko said.

A business forum attended by business leaders from both the United States and Russia will coincide with Obama's visit, Nesterenko said.

(Editing by Philippa Fletcher)