MOSCOW, May 15 (RIA Novosti) - The first round of full-format Russia-U.S. talks on a new strategic arms reduction treaty will be held on May 19-21 in Moscow, a Russian Foreign Ministry official said Friday.

He said they would be "the first substantive discussion" of a new treaty, not "simply an exchange of opinions."

The Strategic Arms Reductions Treaty (START 1), signed in 1991, makes it incumbent on Russia and the United States to reduce nuclear warheads to 6,000 and their delivery vehicles to 1,600 each. The treaty expires on December 5 this year.

Russian President Dmitry Medvedev said last month that any new deal to replace START 1 must also cover delivery systems.

Medvedev and U.S. President Barack Obama agreed at their first meeting in London in April on an immediate start to talks on a new strategic arms reduction treaty.