U.S.-led military action in Libya has bolstered rebels fighting Moammar Gadhafi's forces, but the international operation could continue for months, the Obama administration says.

Ahead of President Barack Obama's national address Monday to explain his decision to act against the Libyan leader, Defense Secretary Robert Gates and Secretary of State Hillary Rodham Clinton said in appearances on the Sunday talk shows that the intervention had effectively rendered Gadhafi's forces defenseless against air attacks and created the conditions for opposition advances westward.