Washington - Russia's military offensive is designed to oust Georgia's democratically-elected government and intimidate other former Soviet states seeking closer ties to the West, Republican presidential hopeful John McCain said Monday.

"This pattern of attack appears aimed not at restoring any status quo ante in South Ossetia, but rather at toppling the democratically- elected government of Georgia," McCain told reporters on the campaign trail in Erie, Pennsylvania.

The conflict that began last week escalated on Monday, as Russian troops in Georgian territory seized a military base outside the breakaway region of South Ossetia.

The Georgian military entered South Ossetia last week to reclaim control over the territory, prompting a swift military response from Russia, which sent troops into South Ossetia to counter the Georgian offensive.

Georgia has called for a ceasefire, but Russia has continued the assault with a series of attacks on Georgian soil and was reportedly preparing a second offensive in another separatist region, Abkhazia.

"That makes Russia's recent actions against the Georgians all the more alarming," McCain said. "In the face of Russian aggression, the very existence of independent Georgia and the survival of its democratically-elected government are at stake."

McCain, 71, read the statement to reporters, trying to show he is vastly more experienced on foreign policy issues than his Democratic rival Barack Obama, who also weighed in on the conflict by calling on both sides to show restraint.

President George W Bush, attending the Olympics in Beijing, said he had spoken with Russian President Dmitry Medvedev and Prime Minister Vladimir Putin and told them the violence was "unacceptable."

"And, look, I expressed my grave concern about the disproportionate response of Russia and that we strongly condemn bombing outside of South Ossetia," Bush told NBC television, a US network. (dpa)