BUCHAREST, Romania —  President Bush won NATO's endorsement Thursday for his plan to build a missile defense system in Europe over Russian objections. The proposal also advanced with Czech officials announcing an agreement to install a missile tracking site for the system in their country.

U.S. Secretary of State Condoleezza Rice called it a "breakthrough agreement" for the military alliance.

"Now it is clearly understood in the alliance that the challenges of the 21st century, the threats of the 21st century, make it necessary to have missile defense that can defend the countries of Europe," Rice told reporters at the NATO summit.

Progress on missile defense represented perhaps the biggest boon to Bush from the NATO summit. Russia has fiercely opposed it.

Rice also noted that NATO has "also asked Russia to stop its criticism of the alliance effort and to join in the cooperative efforts that have been offered to it by the United States."

A NATO statement calls on the alliance to explore ways in which the planned U.S. project, to be based in Poland and the Czech Republic, can be linked with future missile shields elsewhere. It says leaders should come up with recommendations to be considered at their next meeting in 2009.

Despite a setback in his drive to see NATO expanded further eastward to include Ukraine and Georgia, Bush vowed not to drop the issue.

"NATO's door must remain open to other nations in Europe that share our love for liberty and demonstrate a commitment to reform and seek to strengthen their ties with the trans-Atlantic community," Bush said in brief remarks at an alliance meeting. "We must give other nations seeking membership a full and fair hearing."

Fellow NATO leaders, fearing a clash with Moscow, rejected Bush's appeal to allow the former Soviet republics to get on a path toward membership. But Bush's national security adviser, Stephen Hadley, said the president plans to make a new pitch before he leaves office in January. The United States expects to raise the matter at a meeting of NATO foreign minister in December, Hadley said.

The president expressed regret that NATO also declined to offer full membership at this meeting to Macedonia. The invitation was blocked by Greece, which says the country's name implies a territorial claim to a northern region of Greece, also called Macedonia.

"Macedonia's made difficult reforms at home," Bush said. "It is making major contributions to NATO missions abroad. The name issue needs to be resolved quickly so that Macedonia can be welcomed into NATO as soon as possible."

Albania and Croatia were invited to join the alliance, now currently at 26 members.

NATO leaders were adopting a communique stating that "ballistic missile proliferation poses an increasing threat to allied forces, territory and populations." It also will recognize "the substantial contribution to the protection of allies ... to be provided by the U.S.-led system," according to senior American officials, who spoke on condition of anonymity ahead of the statement's release.

Significantly, the document also calls on Russia to drop its objections to the system and to accept U.S. and NATO offers to cooperate on building it, the officials said.

The plan calls for 10 interceptor missiles based in Poland and a tracking radar site in the Czech Republic.

At a news conference in Bucharest on the sidelines of the NATO summit, Czech Foreign Minister Karel Schwartzenberg announced that negotiations with the Americans have been successfully completed and that a deal would be signed in early May. No U.S. official was in attendance, but the Czechs distributed a joint U.S.-Czech statement that said, "This agreement is an important step in our efforts to protect our nations and our NATO allies from the growing threat posed by the proliferation of ballistic missiles and weapons of mass destruction."

The Poles have yet to agree to the plan.

The backing from NATO and the announcement with the Czechs provides Bush with a powerful leg up in his negotiations with Moscow over the issue.

Russia charges the intent of the system would be to weaken its nuclear deterrent capabilities and upset the balance of power in Europe. Bush has repeatedly denied that, saying the facilities are designed to protect Europe against a potential missile attack — or even just nuclear blackmail — by Iran. The dispute has become heated at times, with confrontational, Cold War-style rhetoric from Moscow.

Bush is seeing Russian President Vladimir Putin twice this week — during the NATO summit and in one-on-one meetings planned for this weekend in Sochi, Russia. White House officials have talked optimistically in recent days that the weekend meeting could break the missile defense logjam.

Bush has essentially rejected Russia's suggestion that the U.S. substitute an early warning radar in Azerbaijan for the Europe-based system. But U.S. officials have been working to come up with a list of concessions and assurances that could resolve Moscow's fears, such as offering to let Russia share in the information the system collects and promising not to activate it without a verifiable threat.

Another bright spot for Bush at the summit was the commitment of more troops to Afghanistan's most dangerous areas.

French President Nicolas Sarkozy announced France will send as many as 1,000 troops to the eastern part of the country, freeing up some U.S. forces to move to the south. Canada had threatened to pull its soldiers out of the volatile south, the front line in the fight against a resurgent Taliban and al-Qaida forces, unless it received 1,000 reinforcements from another ally.

"This will meet the Canadian requirement," one official quoted Bush as telling his counterparts at the summit's private morning session.

This issue could have been a major point of contention at the summit. Some Europeans see the NATO mission as largely a humanitarian effort, while Bush and some others regard is a crucial element in the war against terrorism.

As a result, Bush was effusively complimentary of Sarkozy and his policies. The official quoted the president as saying to fellow leaders that the French president's visit to Washington in November had a huge impact on the American people — "like the latest incarnation of Elvis."

Hadley said NATO leaders did not squash all hope for Ukraine and Georgia. They delegated authority to foreign ministers to determine the two countries' progress and then decide themselves at the Brussels meeting in December whether to allow them to take part in so-called membership action plans that are a precursor to joining the alliance, he said.

"It does not have to come back to a NATO summit," Hadley said. "The foreign ministers have been empowered to make the decision."

Hadley predicted a positive decision in December. The official NATO communique stated that Georgia and Ukraine will become members of NATO at point in the future.