They will be joined by Bernard Kouchner, the French foreign minister, who has travelled to Moscow and Tbilisi to push the EU-backed truce.
Rice will then travel on to Tbilisi to underline US support for Georgia.
In a statement made at the White House on Wednesday, Bush said: "The United States of America stands with the democratically elected government of Georgia, insists that the sovereignty and territorial integrity of Georgia be respected," .
"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 keep its word and act to end this crisis."
He said that he expected Russia's armed forces not to hinder the US military's efforts to deliver aid.
Sergei Lavrov, the Russian foreign minister, reacted angrily to Bush's comments, saying that Washington had to choose between its relations with Moscow and its backing of the Georgian government.
"The Georgian leadership is a special project for the United States," Lavrov said.
"At some time it will be necessary to choose between the prestige of this relatively virtual project and partnership on questions that require collective action."
A US C-17 military aircraft arrived on Wednesday in Tbilisi carrying medical supplies, shelter, bedding and cots to Tbilisi.
The US defence department also suggested that it would move to help Tbilisi, saying it will review the needs of the Georgian military, battered during more than four days of all-out fighting with Russian forces over South Ossetia.
Before departing Washington for France and Tbilisi, where she will reiterate US support for the Georgian government, Rice said reports of Russian violations of the ceasefire would "only serve to deepen the isolation into which Russia is moving".
It would also "deepen the very strong, growing sense that Russia is not behaving like the kind of international partner that it has said that it wants to be", she said.
However, in a telephone conversation with Rice on Wednesday, Lavrov said Moscow "strongly rejected insinuations of Russia's 'non-observance' of the principles of resolving" the conflict contained in the French-brokered plan, according to his ministry.
|Rice, centre, will travel to Tbilisi to underline US support [EPA]
Bush said on Wednesday that he had spoken to Nicolas Sarkozy, the French president, and Saakashvili following the peace push by Paris.
Bush, who had spent the morning in the White House "situation room" discussing the crisis with US officials, said "the United States strongly supports France's efforts".
He said Rice would meet Sarkozy before heading to Tbilisi, to "personally convey America's unwavering support for Georgia's democratic government".
"She will continue our efforts to rally the free world in the defence of a free Georgia," he said.
Bush also warned that US support for Russian entry "into the diplomatic, political, economic, and security structures of the 21st century" was "at risk" over Moscow's actions in Georgia.