Mr Fillon raised the plan in a stormy parliamentary debate
France could send "a few hundred" extra troops to Afghanistan, French Prime Minister Francois Fillon has told MPs.
In a stormy National Assembly debate, he rejected opposition Socialist calls for a parliamentary vote on the plan.
French President Nicolas Sarkozy is expected to announce the details of a new deployment to Afghanistan at a Nato summit this week in Bucharest, Romania.
France currently has more than 1,400 troops in Afghanistan, part of the
47,000-strong Nato-led force, Isaf.
He told the National Assembly: "Our armed forces in Afghanistan may invest more in the command structures, particularly in Kabul, in training the Afghan army and in the units in the Afghan provinces.
"The numbers could be something like a few hundred extra soldiers."
An opinion poll on Monday said 68% of French people disapproved of any strengthening of the French troop presence in Afghanistan. Just 15% approved.
Mr Fillon rejected opposition calls for a vote, saying one had not been held when a previous government decided in 2001 to take part in Nato's Afghanistan mission.
But the Socialists warned France risked becoming mired in a "new Vietnam".
Jean-Marc Ayrault, the opposition's leader in the National Assembly, suggested Mr Sarkozy's "Atlantic obsession" of closer ties with the US was behind the plan.
Mr Fillon reiterated French conditions to any new troop deployment, saying there must be faster reconstruction.
He also said by the summer of 2009 the Afghan army had to take responsibility for security around Kabul, where the bulk of French troops are based.
And the French prime minister called on other Nato allies to boost their forces.
Britain and the US have frequently called on other Nato members to send more soldiers to fight the Taleban.
ISAF REGIONAL COMMANDS AND RECONSTRUCTION TEAMS
Countries contributing more than 1,000 troops (1 April 2008):
Australia - 1,100
Germany - 3,490
Italy - 2,360
Netherlands - 1,730
Poland - 1,020
UK - 7,750
US - 19,000