MOSCOW (AP) ― Russia has threatened to deploy missiles to target the U.S. missile shield in Europe if Washington fails to assuage Moscow’s concerns about its plans, a harsh warning that reflected deep cracks in U.S.-Russian ties despite President Barack Obama’s efforts to “reset” relations with the Kremlin.

President Dmitry Medvedev on Wednesday said he still hopes for a deal with the U.S. on missile defense, but he strongly accused Washington and its NATO allies of ignoring Russia’s worries. He said Russia will have to take military countermeasures if the U.S. continues to build the shield without legal guarantees that it will not be aimed against Russia.

The U.S. has repeatedly assured Russia that its proposed missile defense system wouldn’t be directed against Russia’s nuclear forces, and it did that again Wednesday.

“I do think it’s worth reiterating that the European missile defense system that we’ve been working very hard on with our allies and with Russia over the last few years is not aimed at Russia,” said Capt. John Kirby, a Pentagon spokesman. “It is ... designed to help deter and defeat the ballistic missile threat to Europe and to our allies from Iran.”

White House spokesman Tommy Vietor said the United States will continue to seek Moscow’s cooperation, but it must realize “that the missile defense systems planned for deployment in Europe do not and cannot threaten Russia’s strategic deterrent.”

But Medvedev said Moscow will not be satisfied by simple declarations and wants a binding agreement. He said, “When we propose to put in on paper in the form of precise and clear legal obligations, we hear a strong refusal.”

Medvedev warned that Russia will station missiles in its westernmost Kaliningrad region and other areas, if the U.S. continues its plans without offering firm and specific pledges that the shield isn’t directed at its nuclear forces. He didn’t say whether the missiles would carry conventional or nuclear warheads.

In Brussels, NATO Secretary-General Anders Fogh Rasmussen said he was “very disappointed” with Russia’s threat to deploy missiles near alliance nations, adding that “would be reminiscent of the past and ... inconsistent with the strategic relations NATO and Russia have agreed they seek.”

“Cooperation, not confrontation, is the way ahead,” Rasmussen said in a statement.

The U.S. missile defense dispute has long tarnished ties between Moscow and Washington. The Obama administration has repeatedly said the shield is needed to fend off a potential threat from Iran, but Russia fears that it could erode the deterrent potential of its nuclear forces.

“If our partners tackle the issue of taking our legitimate security interests into account in an honest and responsible way, I’m sure we will be able to come to an agreement,” Medvedev said. “But if they propose that we ‘cooperate,’ or, to say it honestly, work against our own interests, we won’t be able to reach common ground.”

Moscow has agreed to consider a proposal NATO made last fall to cooperate on the missile shield, but the talks have been deadlocked over how the system should be operated. Russia has insisted that it should be run jointly, which NATO has rejected.

Medvedev also warned that Moscow may opt out of the New START arms control deal with the United States and halt other arms control talks, if the U.S. proceeds with the missile shield without meeting Russia’s demand.

The Americans had hoped that the START treaty would stimulate progress in further ambitious arms control efforts, but such talks have stalled because of tension over the missile plan.

While the New START doesn’t prevent the U.S. from building new missile defense systems, Russia has said it could withdraw from the treaty if it feels threatened by such a system in future.

Medvedev reaffirmed that warning Wednesday, saying that Russia may opt out of the treaty because of an “inalienable link between strategic offensive and defensive weapons.”

The New START has been a key achievement of Obama’s policy of improving relations with Moscow, which had suffered badly under the George W. Bush administration.

“It’s impossible to do a reset using old software, it’s necessary to develop a new one,” Medvedev’s envoy to NATO, Dmitry Rogozin, said at a news conference.

The U.S. plan calls for placing land- and sea-based radars and interceptors in European locations, including Romania and Poland, over the next decade and upgrading them over time.

Medvedev said that Russia will carefully watch the development of the U.S. shield and take countermeasures if Washington continues to ignore Russia’s concerns. He warned that Moscow would deploy short-range Iskander missiles in Kaliningrad, a Baltic Sea region bordering Poland, and place weapons in other areas in Russia’s west and south to target U.S. missile defense sites. Medvedev said Russia would put a new early warning radar in Kaliningrad.

He said that as part of its response Russia would also equip its intercontinental nuclear missiles with systems that would allow them to penetrate prospective missile defenses and would develop ways to knock down the missile shield’s control and information facilities.