The United States says it will not change its plans for a NATO missile defense system in Europe despite a Russian threat to take counter-measures.

National Security Council spokesman Tommy Vietor said the United States wants cooperation with Russia, but will not in any way limit or change the program. He reiterated that the system is designed to enhance the security of U.S. allies in Europe as well as Russia.

Russian President Dmitry Medvedev said in a televised address Wednesday that Russia will deploy long-range missiles in the southern and western parts of the country if it fails to agree with the United States on its missile shield plan.

Russia has fiercely opposed the plan and wants legal guarantees that the system will not be aimed at Russia.

A spokesmen for the U.S. State Department, Mark Toner, said the U.S. offer to bring Russia into the anti-missile programs stands and that Washington is committed to cooperation with Moscow.

A spokesman for the Defense Department, John Kirby, reiterated that the defense system is designed to help deter and defeat the ballistic missile threat from Iran.

In Brussels, NATO Secretary-General Anders Fogh Rasmussen said he was very disappointed with Russia’s threat to deploy missiles near alliance nations and called for continued dialogue.

The United States wants to build a land- and sea-based missile defense system to protect NATO and its allies against a possible attack from Iran or North Korea. Romania and Poland have agreed to host part of the system and Turkey has agreed to host an early warning radar.

Russia has said that such a system would upset its own nuclear deterrent as well as the strategic weapons balance in Europe.

The Russian president also said Wednesday that Moscow will consider backing out of the New Start disarmament agreement with Washington and other arms control dialogues if the two countries cannot reach an agreement. He also ordered the deployment of a radar missile warning system in the western city of Kaliningrad.

Mr. Medvedev’s comments come a day after the U.S. announced it is halting information-sharing with Russia on non-nuclear military forces in Europe. The announcement follows failed talks between Washington and Moscow on reviving a treaty that limits the number of conventional weapons that could be stationed in Europe. Russia stopped providing information on its forces four years ago.