MOSCOW, July 1 (RIA Novosti) - Russia and the United States have made more significant progress in the preparation of a new strategic arms reduction treaty than the sides expected, a Russian deputy foreign minister said on Wednesday.

"Progress is more significant than we expected when we started the talks on the issue," Sergei Ryabkov said in an interview with RIA Novosti prior to the visit of U.S. President Barack Obama to Russia on July 6-8.

Russian President Dmitry Medvedev and Obama agreed in April to launch discussions on a new agreement to replace the START 1 treaty, which expires in December.

The START 1 treaty obliges Russia and the United States to reduce nuclear warheads to 6,000 and their delivery vehicles to 1,600 each. In 2002, a follow-up agreement on strategic offensive arms reduction was concluded in Moscow. The document, known as the Moscow Treaty, envisioned cuts to 1,700-2,200 warheads by December 2012.

Russia, which proposed a new arms reduction agreement in 2005, expects Washington to agree on a deal that would restrict not only the numbers of nuclear warheads, but also place limits on all existing kinds of delivery vehicles.

Russian and U.S. experts have held three rounds of behind-closed-doors talks on a new deal since April and agreed to report the results at the Russian-U.S. summit in Moscow in July.

Ryabkov said he was almost certain that the sides will be able "to prepare a comprehensive document outlining the verification measures and information exchange procedures, which contain provisions to ensure equal security and significant reduction of strategic offensive weapons through effective verification" by December this year.

The "significant reduction" will be made in comparison to both the START 1 and the Moscow Treaty, the diplomat added.

According to a report published by the U.S. State Department in April, as of January 1 Russia had 3,909 nuclear warheads and 814 delivery vehicles, including ground-based intercontinental ballistic missiles (ICBM), submarine launched ballistic missiles (SLBM) and strategic bombers.

The same report said the United States had 5,576 warheads and 1,198 delivery vehicles.