ROME, September 12 (RIA Novosti) - Russia and the United States have fundamental differences on a new agreement that is to replace the Strategic Arms Reduction (START) Treaty, a senior Foreign Ministry official said Wednesday.

Russian and U.S. delegations are conducting consultations in Rome to work out a new deal to replace the current START treaty, which expires December 5, 2009.

"Unfortunately, our differences are very serious. They concern the substance of a future accord. So far, we have been unable to convince the U.S. that a new document should be legally binding," Anatoly Antonov, director of the Foreign Ministry Security and Disarmament Department, said in an interview with RIA Novosti.

He said the Russian side hopes that solutions will be found in the course of further consultations.

"We will work until the last moment in an effort to reach an agreement that would respond to the interests of our two countries," he said.

The START I treaty was signed July 31, 1991, five months before the collapse of the Soviet Union, and expires December 5, 2009.

It remains in force as a treaty between the U.S., Russia, Belarus, Kazakhstan and Ukraine. Belarus, Kazakhstan and Ukraine have since totally eliminated their strategic arms capabilities, and the U.S. and Russia reduced the number of delivery vehicles to 1,600, with no more than 6,000 warheads.

The treaty was followed by START II, which banned the use of multiple re-entry vehicles (MIRV) but never entered into force and was later bypassed by the Treaty on Strategic Offensive Reductions (SORT), signed by Vladimir Putin and George W. Bush in Moscow May 24, 2002.

Russia and the U.S. earlier confirmed plans to reduce their strategic arms to a minimum possible level and to develop new agreements on START.

Russia's foreign minister and the U.S. secretary of state said in a statement in June that Russia and the U.S. have confirmed their intention to minimize their strategic offensive arms and to develop relevant agreements.