On Friday Michele Alliot-Marie, the defence minister, said: "I can't let it be said or implied that France is not doing its duty in the Lebanese crisis."
Meanwhile, Germany's foreign minister has underlined his country's offer of a "strong maritime component" to the force.
France, which currently leads the Unifil force in southern Lebanon, said on Thursday it was doubling its contingent to 400 troops.
Many of the new troops are to set off for the Middle East on Sunday.
The size of France's contribution was a disappointment to some at the UN who had expected more French soldiers, though it did not dissuade countries from pledging a total of 3,500 troops for the expanded force during a meeting on Thursday in New York.
A spokesman for the foreign ministry reiterated on Friday that France could always send additional troops at a later stage.
Denis Simonneau said that "depending on the ongoing discussions, we will decide on the way in which we participate in the reinforced Unifil in the long term".
The defence minister noted that France was willing to continue leading the force as it expands from the current 2,000 troops to as many as 15,000.
France and Italy - another potential European contributor - have said the peacekeeping mandate is not explicit enough, and demanded the UN set clear rules of engagement for troops in the force.
Frank-Walter Steinmeier, the German foreign minister, said in Berlin on Friday that his country was discussing how it could help advise and equip Lebanese border officials.
He spoke after meeting with the foreign affairs committee of parliament, which will have to approve any deployment.
Chancellor Angela Merkel said on Thursday night that Germany would not send combat troops.
Germany is concerned about
clashes with Israeli troops
Germany instead is prepared to offer "a strong maritime component to control the supply of weapons to Lebanon by sea" and ensure that Hezbollah is not supplied with arms by ship, Steinmeier said.
He stressed, however, that Germany does not plan to send officers to patrol the Lebanese-Syrian border.
That, he said, "has neither been sought by Lebanon nor suggested or approved by the German government".
"We are in talks with the Lebanese government on what else, for example at the airport in Beirut, we can do to support Lebanese border protection," Steinmeier said.
"This is about advisory services, technical equipment and optimising border controls."
Encouraging news came from Italy on Friday when its centre-left government formally approved the deployment of soldiers to Lebanon.
A cabinet meeting did not specify the size of the Italian contingent but officials say Rome is ready to deploy up to 3,000 troops. That would make it one of the biggest contributors.
"Italy wants to make its contribution to peace," Romano Prodi, the Italian prime minister, told a news conference after the special meeting of ministers.
Arturo Parisi, the defence minister, said in a written statement for parliament that "eventually our country could assume the responsibility of leading the operation", though Prodi has not yet talked of Italy taking command.
The move was later approved by the joint defence and foreign relations committees of both house of parliament.