"We've agreed to help the French with airlift. And we're now working out the details," a defense official, who spoke on condition of anonymity, told AFP.
However, there was still no final approval on a request from Paris to help refuel French warplanes with American tanker aircraft, he and another defense official said.
The US government had already agreed to bolster intelligence sharing to assist the French, including information from surveillance drones and spy satellites, officials said. US Secretary of State Hillary Clinton confirmed the move to put intelligence resources and transport planes at the disposal of French troops.
"We are supporting the French operation in Mali with intelligence and airlift," she said in Washington after meeting Somali President Hassan Sheikh Mohamud. The American transport planes would likely be used to ferry French tanks, armored vehicles and other heavy equipment.
The United States has a vast fleet of military transport planes at a network of bases in Europe and elsewhere, along with refueling tankers, which are in increasingly short supply in France and other NATO countries.
'Every time I turn around, I face a group of lawyers.'
Since the French launched its armed intervention last week against advancing Islamist fighters in Mali, President Barack Obama's administration has hesitated to give a green light to logistical support, partly due to a policy dilemma.
Since Malian military officers staged a coup last March, the US administration had suspended any direct aid to the new leadership until democracy was fully restored.
US Defense Secretary Leon Panetta referred to legal considerations when he was asked by reporters about Washington's deliberations on delivering assistance to the French.
"One thing I've learned is every time I turn around, I face a group of lawyers. And it's no different now," Panetta said Wednesday during a visit to Rome.