The Kremlin is playing down hopes of a breakthrough on reducing nuclear arsenals ahead of a visit to Moscow by the U.S. president, linking arms cuts with U.S. plans to deploy a missile defense system in Central Europe.

The United States and Russia are negotiating a nuclear disarmament treaty to replace the Strategic Arms Reduction Treaty, or START I, which is due to expire on Dec. 5.

The visit of U.S. President Barack Obama to Moscow from July 6 to 8 is not likely to trigger a major announcement on ongoing arms control talks or on other issues, the Kremlin said in a statement posted Friday on its web site.

"We are pragmatic. We do not have high expectations of the outcome of the visit," the Kremlin statement said. "The process of improving relations will take time and honest effort on both sides," it said, acknowledging that the United States was trying to improve relations.

But Moscow will not reduce its own nuclear potential until there is clarity on Washington's plans for a missile defense system in Central Europe, General Nikolai Makarov, head of the military's General Staff, said in separate comments Friday. "So long as the situation in the world is not clear, including on the missile defense system, we will not touch our nuclear potential," Makarov said, in a reference to U.S. plans to install interceptor missiles in Poland and a radar base in the Czech Republic.

"The question of strategic nuclear forces for us is sacred. We will provide as many resources as are needed to maintain stability in the world," he said. "We will leave our strategic missile forces practically unchanged."

A U.S. administration official declined to comment on Makarov's comments. On a conference call with reporters after Obama held talks with German Chancellor Angela Merkel, the official said he had just read the report and said it would not be prudent to say anything.