Citing unnamed US officials, the newspaper said the events in Mali and neighboring Algeria have prompted sharp debate within President Barack Obama's administration over whether these radicals present enough of a risk to warrant a military response.

Islamist militants associated with Al-Qaeda have seized control of a significant part of northern Mali, prompting France to launch a military operation there a week ago to prevent the rebels from capturing Bamako, the capital.

French Defense Minister Jean-Yves Le Drian said Friday that Paris had increased its troop numbers by 400 in a single day, from 1,400 Thursday to 1,800, "and the progress on our presence on the ground continues."

France plans to deploy 2,500 soldiers in the country.

As they watch these events unfold, some top Pentagon officials and military officers warn that without more aggressive US action, Mali could become a haven for extremists, akin to Afghanistan before the terrorist attacks of September 11, 2001, the report said.

But many top White House aides say it is unclear whether the Mali insurgents, who include members of Al-Qaeda in the Islamic Maghreb (AQIM), could threaten the United States, the paper said.

Those aides worry about being drawn into a messy conflict against an elusive enemy in Mali just as US forces are withdrawing from Afghanistan, it noted.

"No one here is questioning the threat that AQIM poses regionally," the paper quoted one administration official as saying. "The question we all need to ask is, what threat do they pose to the US homeland? The answer so far has been none."