CRAWFORD, Texas — President Bush sent a stern warning to Russia today that it cannot lay claim to two breakaway provinces in neighboring Georgia, an American ally. “No room for debate on this point,” the president said.

Searching for signs of progress, Mr. Bush said President Medvedev’s signing today of a cease-fire plan was “an important development. That’s a hopeful step,” Mr. Bush told reporters at his ranch. “Russia now needs to honor that agreement” and withdraw forces from the much smaller former Soviet state.

The Russian foreign minister said Thursday that Georgia could “forget about” getting back the two separatist regions, South Ossetia and Abkhazia. Mr. Medvedev also met with their leaders in Kremlin this past week, raising the prospect that Moscow could absorb the regions even though the territory is internationally recognized as being within Georgia’s borders.

Mr. Bush disputed the claim that two areas may not be part of Georgia’s future. They are of Georgia now, he said at the ranch, and reaffirmed that they are within recognized borders. There is “no room for debate on this,” the president said.

Secretary of State Rice, who briefed Mr. Bush after a quick trip to Georgia, said that “when it is resolved, I mean the underlying conflict, it must be resolved on the basis of the territorial integrity of Georgia.”

The cease-fire agreement calls for both forces to pull back to positions they held before fighting erupted August 8. That was when Georgia launched a massive barrage to try to take control of the Russian-backed separatist region of South Ossetia. The Russian army quickly overwhelmed the forces of its small American-backed neighbor, and Moscow’s troops drove deep into Georgia.

“The world has watched with alarm as Russia invaded a sovereign neighboring state and threatened a democratic government elected by its people,” Mr. Bush said in his weekly radio address. “This act is completely unacceptable to the free nations of the world.”

Keeping up the diplomatic pressure, Ms. Rice planned to go to Brussels next week for meetings with the foreign ministers of NATO allies and European Union officials.

The crisis has chilled relations between America and Russia. The fighting comes as America is sealing the deal on a missile shield in Europe — an issue already unraveling ties between the two former Cold War foes.

Poland and America signed a deal Thursday for Poland to accept a missile interceptor base as part of a system America says is aimed at blocking attacks by adversaries such as Iran.

Moscow feels it is aimed at Russia’s missile force. A Russian general was quoted by Interfax News Agency yesterday as saying that by accepting an American missile defense battery, Poland was “exposing itself to a strike.”

The missile deal awaits approval by Poland’s parliament and signing by Ms. Rice during a future visit to Warsaw, possibly in the week ahead.

That is sure to further antagonize Russia. But America wants to be careful to alienate Moscow and drive Russian leaders away from further integration with the West.

“Russia’s actions in Georgia raise serious questions about its role and its intentions in the Europe of the 21st century,” Mr. Bush said. “In recent years, Russia has sought to integrate into the diplomatic, political, economic, and security structures of the West. The United States has supported those efforts. Now Russia has put its aspirations at risk by taking actions in Georgia that are inconsistent with the principles of those institutions.

“To begin to repair the damage to its relations with the United States, Europe, and other nations, and to begin restoring its place in the world, Russia must act to end this crisis.”

So far, the White House has hedged on saying what consequences Russia might face.