"This is not 1968," said US Secretary of State Condoleezza Rice emphatically at a Washington news conference, "where Russia can threaten a neighbour, occupy a capital, overthrow a government and get away with it."
By Richard Lister
BBC News, Washington
Russia has deployed thousands of soldiers to the region
Things, she said, have changed.
Certainly, the US had very few options for countering Soviet tanks when they rumbled into Prague almost exactly 40 years ago.
But the present crisis suggests there is no easy solution for the West this time either.
On a whole range of issues now, from the "War On Terror" to missile proliferation, to the nuclear threat from Iran, the US has been doing its utmost - over many years - to strike a partnership with Moscow.
Throw in Russia's growing wealth, influence and confidence and American threats to isolate Moscow begin to sound a bit hollow.
So, for now, the broader question of US-Russian relations is being put to one side, while officials from the president down focus on how to contain the trouble in Georgia.
Sending out signals
The US humanitarian mission serves a range of purposes.
The first air shipment of US aid landed in Tbilisi on Wednesday
As well as providing aid to many thousands of displaced Georgians, it also sends a range of political messages.
It goes some way to responding to the concerns of many Georgians who believe Uncle Sam was not there for them when they needed him, and it tells the Russians that Washington is not backing away from the country it has described as a "beacon of democracy".
There is something of a military subtext too.
The US is to use its navy and air force for this mission and warned the Russians that they must keep all transport infrastructure open.
So, no more blocking major roads and no interference with ports or airspace.
There is no hint whatsoever that the US would be prepared to use military force against the Russians - far from it.
But bringing American forces into the equation on the ground is an implicit warning to the Russians to back off.
No one wants an accidental confrontation which could turn into something worse.
Russia or Georgia?
Beyond the humanitarian mission though, the Pentagon has confirmed that it will be assessing Georgia's wider military needs in the wake of the losses suffered at the hands of the Russians.
Mr Bush received an ecstatic greeting when he visited Tbilisi in 2005
It has already helped revamp and re-train Georgian forces, provided more sophisticated military equipment and updated bases to meet Nato standards.
Of course, those moves may well have contributed to Russia's decision to re-assert its authority in the region in the first place.
So as well as re-assessing its relationship with Russia, Washington will have to look again at whether its policy of bolstering Georgia's independence has been entirely successful, and whether it can continue exactly the same policy in the same way while still pursuing a strategic partnership with Moscow.
Certainly the Russians believe the US faces a choice.
"At some time," said the Russian Foreign Minister, Sergei Lavrov, "it will be necessary [for the US] to chose between supporting this virtual project [Georgia] and real partnership [with Russia]".
US Secretary of State Rice rejected that as a false choice and accused some in Russia of harking back to the days of the Cold War.
But Russia is not alone in wanting to entrench its influence.
The North Atlantic powers are trying to do the same in Russia's old back yard, and Russia has clearly decided enough is enough.
Ultimately, with just a few months left of his term in office, that is a long-term problem which President Bush will be leaving on the top of his successor's in-tray.