MOSCOW (AFP) - Russia could withdraw from a Cold War-era treaty limiting short and medium-range missiles if the United States places a missile defense system in the Czech Republic and Poland, the head of the armed forces said on Thursday.

General Yury Baluyevsky told Russian news agencies that Moscow or Washington were entitled to withdraw from the Intermediate-Range Nuclear Forces Treaty, commonly known as INF, if there was "convincing proof" of the need to do so.

With several countries currently developing medium-range missiles, "such proof exists," he told Interfax.

He said Russia's decision could hinge on U.S. plans to build a missile defense shield in central Europe -- plans that Moscow strongly opposes.

"We will see how our American partners act in future. What they're doing today, creating an... anti-missile defense region in Europe, is inexplicable," said Baluyevsky.

At an international security conference on Sunday, Russian Defense Minister Sergei Ivanov called the INF treaty, signed by the Soviet Union and the United States in 1987, a "relic" of the Cold War, saying that other countries were developing such weapons while Washington and Moscow's hands were tied.

In Washington, State Department spokesman Sean McCormack said the U.S. had received no formal notice from Moscow about withdrawing from the INF but was "still looking into the specific provisions" of the treaty concerning an eventual pullout.