Tbilisi, Georgia —- Russian forces broadened their crushing offensive against Georgia on Monday, and Georgian officials feared that the Russian invasion would mean the end of their country's independence.

Russian troops were reported in control of Georgia's main east-west highway outside the central Georgian town of Gori, had taken control of Georgia's main port at Poti, seized a Georgian military base in the west and dominated the skies, bombing and strafing retreating Georgian troops.

In Washington, President Bush warned of a "dramatic and brutal escalation" by Russia and said it appeared Russia might be trying to oust Georgia's president, Mikhail Saakashvili, a former Washington lawyer who is a staunch U.S. ally.

Speaking in the White House Rose Garden immediately after flying home from China, Bush said it appeared Russia was moving beyond the original "zone of conflict" and might soon bomb the civilian airport and attack Georgia's capital, Tbilisi.

Saakashvili, in a nationally broadcast address, said he had offered a cease-fire but had been rebuffed.

Russian officials said Georgian forces were still fighting, however, and a Russian defense spokesman said Saakashvili's offer was not "worth a penny."

Col. Gen. Anatoly Nagovitsin, the deputy head of the Russian military's general staff, reiterated his government's bottom line: Russia will not cease fighting until Georgia not only pulls out of the breakaway provinces of South Ossetia and Abkhazia but also signs an agreement never to pursue force against them again.

The United States and Europe pressed for a cease-fire, without effect. Secretary of State Condoleezza Rice conferred by telephone with foreign ministers from the world's largest economic powers, who also urged Russia to accept a cease-fire and international mediation.

Russian Prime Minister Vladimir Putin chafed at the criticism, likening Russia's moves against Georgia to the U.S.-led invasion of Iraq and using the American presence there as justification for Russian calls for the overthrow of the U.S.-allied Georgian government.

"Of course, Saddam Hussein ought to have been hanged for destroying several Shiite villages," Putin said from Moscow. "And the incumbent Georgian leaders who razed 10 Ossetian villages at once, who ran over elderly people and children with tanks, who burned civilians alive in their sheds —- these leaders must be taken under protection."

He also criticized the United States for flying 2,000 Georgian troops home from Iraq aboard U.S. military aircraft.

What began as a Georgian offensive last Thursday to wrest control of the Russia-backed South Ossetian region by Monday had grown into a punishing display of Russia's military superiority.

"We have never been and will never be a passive observer in the region," said Russia's president, Dmitry Medvedev, according to state newswires.

The Russian government accused the Georgian military of a barbaric campaign against separatists in South Ossetia and Abkhazia, saying that as many as 2,000 civilians have been killed in the fighting. The Georgians put the numbers much lower.

Thousands of refugees fled South Ossetia to Russia during the past week. Georgia countered that the violence is the result of Russian aggression, aimed at destabilizing Saakashvili.

On Sunday, Russian tanks and jets pounded Georgian troops until they evacuated Tskhinvali, South Ossetia's capital. On Monday, Russian tanks moved to the edge of South Ossetia and toward Georgian-controlled villages there, according to Georgian troops who witnessed the fighting.

Russian aircraft hit the city of Gori, the home of a Georgian military base that sits between Tskhinvali and Tbilisi. Early today, Elene Agladze, who works in the office of the Georgian director of national security, said Russian troops were reported on the outskirts of Gori.

Asked if there were fears that the Russians could plow on to Tbilisi, Agladze said, "with Russians, fear is always there."

Georgian officials said Russian troops on Monday also moved beyond the western region of Abkhazia into Georgian-controlled areas, seizing a military base and strengthening a second flank that appeared to be squeezing toward Tbilisi.

The leader of Abkhazia, Sergei Bagapsh, told Russian state news agencies that his forces offered a corridor of escape to Georgian soldiers. "But if they refuse to use it," he said, his men would destroy the Georgians.

Vladimir Pribylovski, the head of a Moscow research center, said that Russian officials were teaching Saakashvili a lesson after his military went after Russia's allies in South Ossetia.

"He miscalculated: He did not expect that Moscow would rap his knuckles. He thought it would just stick to rhetoric," Pribylovski said. "But the Kremlin risked giving him a thrashing and is quietly celebrating now."