Morin said Nicolas Sarkozy, France's president, had written a letter to his Nato counterparts, requiring any enhanced French role to be considered as part of a "global approach" to the problems there.
The defence minister said: "Even if you have military control, it's not enough. There has to be an accompanying plan that allows the Afghans to progressively create the conditions of their own development, and thus their own autonomy, and to take their destiny in their hands."
He said France had not yet decided how it will boost its contribution to the Afghan mission beyond the 1,500 troops it has there already.
Most of these operate in the capital, Kabul, and its northern suburbs.
France's decision is expected at a Nato summit in Bucharest, the Romanian capital, next week.
Morin declined to confirm newspaper reports in both Britain and France in recent days saying France's government would contribute about 1,000 more troops.
"There is no figure," he said.
There has been widespread speculation about where the new French troops would be deployed, such as in southern Afghanistan, where much of the fighting against the Taliban occurs, or in another area such as the east, along the border with Pakistan.
Morin appeared to suggest, however, that Paris would not enter the south, saying "we naturally have more of an interest" in possibly avoiding zones where France is not present now.
A deployment to the east would be more contiguous with its forces in the Afghan capital.
Canada had warned that it would pull out its 2,500 troops from Afghanistan if other Nato allies do not offer more help and has called for 1,000 more soldiers.
Nato has been under considerable strain for some time with a revived Taliban campaign in Afghanistan.
More than 8,000 people died in violence there last year, the highest annual toll since the US-led removal of the Taliban government in 2001.