Russian President Dmitry Medvedev warned in an interview Monday that he could walk away from a nuclear disarmament treaty signed last week if a US missile defense program in Europe creates "imbalance."

Medvedev said former Cold War foes Russia and the United States negotiated specific language in the preamble of the new START treaty he signed last week with US President Barack Obama.

This "formula" states that there is an "interconnection between the strategic offensive arms and missile defense," Medvedev told ABC News.

"So if those circumstances will change, then we would consider it as the reason to jeopardize the whole agreement."

If the United States "radically multiplies the number and power of its missile defense system, obviously that missile defense system is indeed becoming a part of the strategic offensive nuclear forces, because it's capable of blocking the action of the other side," he added.

"So an imbalance occurs, and this would be certainly the reason to have a review of that agreement."

Obama's Republican foes have cautioned they will oppose the pact if it hampers the US missile defense plans bitterly opposed by Russia. The issue had been a main point of contention during months of arduous negotiations between the two countries.

They have also warned that Obama must submit a comprehensive plan for upgrading US nuclear laboratories and modernizing the US nuclear arsenal before senators take up the treaty, which must be ratified by the US Senate and Russia's parliament, or Duma.

Medvedev said that while Russia might consider bringing a "premature end" to the agreement if it feels threatened by the US missile defense program, he hopes "something like that would not happen" and the two sides would consult one another.

The new START slashes limits on the number of deployed warheads by 30 percent from levels set in the last major US-Russian disarmament treaty in 2002, specifying limits of 1,550 nuclear warheads for each of the two countries.

The ABC interview was conducted on Friday, a day after Medvedev and Obama signed the nuclear arms reduction treaty in Prague. It first aired on Monday.