WASHINGTON - Scrambling to find ways to punish Russia for its invasion of pro-western Georgia, the United States and its allies are considering expelling Moscow from an exclusive club of powerful countries and cancelling an upcoming joint NATO-Russia military exercise, U.S. officials said Tuesday.

But with little leverage in the face of an emboldened Moscow, Washington and its friends have been forced to face the uncomfortable reality that their options are limited to mainly symbolic measures, such as boycotting Russian-hosted meetings and events, that may have little or no long-term impact on Russia's behaviour, the officials said.

With the situation on the ground still unclear after Russian President Dmitri Medvedev on Tuesday ordered a halt to military action in Georgia, U.S. officials were focused primarily on confirming a ceasefire and attending to Georgia's urgent humanitarian needs following five days of fierce fighting, including Russian attacks on civilian targets.

At the same time, however, President George W. Bush and his top aides were engaged in frantic consultations with European and other countries over how best to demonstrate their fierce condemnations of the Russian operation that began in Georgia's separatist region of South Ossetia, expanded to another disputed area, Abkhazia, and ended up on purely Georgian soil.

"The idea is to show the Russians that it is no longer business as usual,'' said one senior official familiar with the consultations among world leaders that were going on primarily by phone and in person at NATO headquarters in Brussels where alliance diplomats met together and then with representatives of Georgia.

For now, the Bush administration decided to boycott a third meeting at NATO on Tuesday at which the alliance's governing board, the North Atlantic Council, was preparing for a meeting with a Russian delegation that has been called at Moscow's request, officials said.

On the table for future action is the possible cancellation or U.S. withdrawal from a major NATO naval exercise with Russia that is scheduled to begin Friday, the officials said. Sailors and vessels from Britain, France, Russia, and the U.S. were to take part in the annual Russia-NATO exercise aimed at improving co-operation in maritime security.

The exercise, which is being hosted by Russia this year, began a decade ago and typically involves around 1,000 personnel from the four countries, the officials said.

In the medium term, the United States and its partners in the Group of Seven, or G7, the club of the world's leading industrialized countries that also includes Britain, Canada, France, Germany, Italy and Japan, are debating whether to effectively disband what is known as the G8, which incorporates Russia, by throwing Moscow out, the officials said.

The officials spoke on condition of anonymity because no decisions have yet been made and consultations with other countries involved are still ongoing.