President Dmitry Medvedev said Wednesday that Russia will deploy new missiles aimed at the American missile defense system in Europe if it does not go ahead with an agreement with Washington and NATO on how the systems will be built.

The American missile defense plan dates back to the Reagan Administration and was revamped two years ago into a proposed system of interceptors based on land and at sea around Europe, the Washington Post reported -- a plan Russia considers a threat to its nuclear forces.

Meanwhile, President Barack Obama and his administration maintain that the plans are designed to thwart any potential threat from Iran.

Accusing the United States of failing to consider Russian concerns, Medvedev, in a televised address, said there is still time for an agreement.

The United States and its NATO partners as of now aren't going to take our concerns about the European missile defense into account, Medvedev said.

If the situation does not develop well, then Russia reserves the right to halt further steps in disarmament and the corresponding weapons controls.

One of these steps could the installation of Russian missiles in its westernmost Kaliningrad region and other areas of Russia. Romania and Poland have agreed to host part of a revamped U.S. missile shield. Medvedev also warned that Russia will deploy short-range Iskander missiles in Kaliningrad, a Baltic Sea exclave bordering Poland and Lithuania.

A failure to come to an agreement may also result in Russia quitting the Strategic Arms Reductions Treaty, or START, for nuclear arms cuts with the U.S.; Medvedev signed that treaty with Obama in April 2010.

There could be a basis for our exit from START. This is allowed under the sense of the treaty itself, Medvedev said.

The missile warning comes as Medvedev prepares to step aside so that he and current Prime Minister Vladimir Putin can switch roles. Medvedev will be leading the United Russia party in the December parliamentary elections, and Putin says he will anoint him prime minister, The Associated Press reported.