The Obama administration is considering significant military backing for France’s drive against al-Qaeda-linked militants in Mali, but its support for a major ally could test U.S. legal boundaries and stretch counterterrorism resources in a murky new conflict.

The United States is already providing surveillance and other intelligence help to France and may soon offer military support such as transport or refueling planes, according to U.S. officials, who stressed that any assistance would stop short of sending American combat forces to the volatile West African nation. …

Direct military aid to Mali is forbidden under U.S. law because the weak rump government there seized power in a coup. U.S. moves are further complicated by uncertainty about which militants would be targeted in an assault.

The loosely affiliated web of Malian militants in the country’s north includes members of al-Qaeda in the Islamic Maghreb (AQIM). But other fighters are longtime foes of the Malian government and pose no direct threat to U.S. interests.