The United States has chosen to play a cautious supporting role to France’s military action against rebel fighters in Mali, after Washington’s own attempt to build up the African nation’s army backfired badly. While the Pentagon promised transport planes, refueling tanker aircraft and spy planes to back up France’s intervention in Mali, officials made clear President Barack Obama was deeply reluctant to plunge America into a fresh war against insurgents. “I think the United States was very cautious not to get involved in another complex operation, which is sold as easier than it actually is,” Stephanie Pezard, a scholar at the RAND corporation said. “It didn’t want to be bogged down on another front that’s maybe not of the highest strategic interest either,” she added. But the French military action also raised questions about a much-touted US policy that hopes to counter terror groups in Africa and elsewhere by bolstering foreign armies with advice from elite American specialforces.