PRAGUE, Czech Republic (AP) - The United States and leaders of the Czech Republic agreed Tuesday to place a radar system in this former Soviet satellite that would warn of long-range missiles coming to Europe from the Middle East.

But Secretary of State Condoleezza Rice turned old Cold War rhetoric away from Moscow and toward Tehran as she signed the first solid treaty in what have been difficult negotiations.

Iran looms as an ever-larger threat and the next U.S. president is unlikely to walk away from the missile defense system the Bush administration is trying to establish in Eastern Europe, Rice said.

"We face with the Iranians, and so do our allies and friends, a growing missile threat that is growing ever longer and ever deeper and where the Iranian appetite for nuclear technology to this point is still unchecked," Rice said after signing the Czech agreement. "It's hard for me to believe that an American president is not going to want to have the capability to defend our territory (and) the territory of our allies."

The proposed U.S. missile defense system calls for a tracking radar in the Czech Republic and 10 interceptor missiles in Poland. Moscow has threatened to aim its own missiles at any eventual base in Poland or the Czech Republic.

Shortly after the treaty was signed, Russia's Foreign Ministry said Moscow would be forced to initiate a military response if the deal goes ahead.

If the agreement is ratified, "we will be forced to react not with diplomatic, but with military-technical methods," the Foreign Ministry statement said. It did not give specifics of what the response would entail. In February, then-President Vladimir Putin said that if the plan advances, Russia could aim missiles toward prospective missile defense sites and deploy missiles in the Baltic Sea region, which borders Poland.

President Bush discussed U.S. missile-defense plans with the new Russian president, Dmitry Medvedev, earlier this week during an economic conference of world leaders in northern Japan. Medvedev later told reporters that his hour-long chat with Bush yielded "no particular progress" on issues dividing the countries, particularly the missile shield.

White House national security spokesman Gordon Johndroe, with Bush in Japan, said early Wednesday: "As President Bush said to President Medvedev, we seek strategic cooperation on preventing missiles from rogue nations, like Iran, from threatening our friends and allies."

"We want to design a system between the United States, Russia and Europe, with everyone participating as equal partners," Johndroe added.

Largely untested, expensive and unpopular among large majorities of the former East Bloc nations where it would be based, the theoretical missile shield also represents a potential foreign policy success that the Bush administration could pocket in its waning months.

The Bush administration is trying to arrange deals before Bush leaves office in January.

Talks with Poland had bogged down recently over Polish demands for billions of dollars worth of U.S. military aid, in part to deter a possible strike from a peeved Russia.

Rice, however, said the United States and its allies would proceed.

"Ballistic missile proliferation is not an imaginary threat," Rice said after meeting Czech Prime Minister Mirek Topolanek. She said Iran continues to perfect the tools it might one day use to build a bomb, along with long-range missiles that could carry a warhead.

Fielding the system will take years and the winner of this fall's U.S. presidential election will have to decide whether to go ahead with the project. Republican John McCain is a supporter; Democrat Barack Obama has been more circumspect.

"I'm not going to get involved in the politics, but here's the case for missile defense," Rice said in preface to a lengthy discussion of what she claimed are the project's early successes and ultimate worth as a deterrent to a bellicose and unpredictable Iran. Rice said similar anti-missile technology was deployed when North Korea test-fired long-range missiles two years ago and she cited the successful U.S. destruction of an errant satellite this year.

Rice said the shield is a good deal for the Czech Republic and for Poland, where the United States hopes to place another part of the system, although Warsaw hasn't yet agreed. The deal is far from done even in Prague, where the treaty signed Tuesday must be put to a vote in Parliament and where a second pact is still under negotiation.

Rice lobbied members of the Czech parliament directly Tuesday.

"This treaty will not only increase security of the Czech Republic but also of Europe" and beyond, said Czech Foreign Minister Karel Schwarzenberg.

"I believe there will be enough members of Parliament who are aware of their responsibility and will vote for the agreement," Schwarzenberg said.

Only about a third of Czechs say they support the deal. Hundreds gathered in a Prague downtown square to protest the agreement, waving banners with slogans such as "It's not over yet," and "Condoleezza is not welcome!"

"The agreement between the Czech and the U.S. government is consistent with the attitude of Czech government which completely ignores the will of about 70 percent of Czech population," said Jan Tamas, an organizer of the rally.

"We believe it's not right for a democratic society when the government goes clearly against the will of the majority of people and that's why we're here today to protest against that."

Rice had hoped to make the week's visit in Eastern Europe a clean sweep for the defense system, but said earlier Tuesday the Poles are not ready to sign a similar agreement now and there was little point in visiting Warsaw until the government there makes a move.

The United States has answered Polish demands for military hardware and the final agreement rests with Polish authorities, Rice said.

That marks a setback from last week when U.S. negotiators thought they had the outline of a deal. Warsaw rebuffed that tentative deal Friday, in strong language that U.S. diplomats said came as a surprise.

U.S. and Polish officials said talks would continue.

Associated Press Writer Karel Janicek contributed to this report.