French President Jacques Chirac has poured cold water on US calls to expand Nato's role in Iraq.
The US wants to bolster the coalition in the face of violent unrest in Iraq
Mr Chirac was responding to President George W Bush's remarks that the Nato alliance should become more involved after the 30 June handover of power.
He said he did not believe it was Nato's mission to intervene, or that such a move would be well understood.
Later, Mr Bush's national security adviser stressed the US president had not been requesting additional troops.
Speaking in a BBC interview, Condoleezza Rice said some additional foreign troops might be brought in for specific tasks, but large-scale foreign deployments would detract from the main priority: to build up the Iraqi security forces.
Nato currently has no formal role in the occupation of Iraq.
On Tuesday, the UN Security Council unanimously voted for a UK and US-backed resolution on transferring power to an Iraqi government.
Mr Bush made the statement at the G8 summit in the US state of Georgia, where he is meeting, among others, the French and German leaders.
He said that while many Nato members were part of the US-led coalition in Iraq he felt the alliance's role could be expanded.
"We believe Nato ought to be involved," Mr Bush said
after a breakfast meeting with Mr Blair
outside the G8 summit venue.
"We will work with our Nato friends to at least continue the
role that now exists and hopefully expand it somewhat," he said.
But the French president said Nato operations were only possible if explicitly requested by the new Iraqi government.
"I see myself with strong reservations on this initiative," Mr Chirac said.
The BBC News Online world affairs correspondent Paul Reynolds says that although France has never been expected to play any military role in Iraq, President Chirac's comments again show the underlying divisions over the role of foreign troops there.
President Bush's message might have been meant for more sympathetic Nato countries, he says, though a number are already in Iraq. What the US and UK want is a country or countries to provide troops to protect UN personnel in Iraq.
Sets 30 June 2004 as date for end of occupation and dissolution of the Coalition Provisional Authority
Envisages direct democratic elections to a Transitional National Assembly no later than 31 January 2005
Provides for "full partnership between Iraqi forces and the multinational force"
Acknowledges need to confer on "sensitive offensive
Firmly places Iraqi security forces under Iraqi control
But a senior British official said this week that "no significant steps" would be taken towards increasing Nato's role.
France and Germany are key members of Nato, and as recently as April, turned down a request for a greater Nato role in Iraq on the grounds that the alliance was already overstretched in the Balkans and Afghanistan.
Earlier Mr Bush called the passing of the UN resolution a "great victory" for Iraq, while UK Prime Minister Tony Blair said rebels there now faced a "united world".
The plan formalises ties between Iraq's future government and foreign forces.
It was adopted after many revisions by the 15-member Security Council, where opposition to the US-led invasion of Iraq has been strong.
Resolution 1546 sets out the powers and constraints for the new interim Iraqi government, due to take power from the US administration on 30 June.