ABIDJAN, Ivory Coast - The United States warned Laurent Gbagbo that he faces sanctions if he continues to refuse to step down as president after a disputed election that the United Nations says was won by his opponent.

The African Union, meanwhile, suspended Ivory Coast's membership Thursday in the latest sign of growing pressure against the country's former president.

Gbagbo has not spoken publicly since his rushed inauguration over the weekend, after rejecting the results released by his country's electoral commission. The results showed that opposition leader Alassane Ouattara had won by a nearly 10-point margin. Those results were certified by U.N. officials, who declared that Ouattara had won by "an irrefutable margin."

The country has been on edge since the results were released last week. Since then, Gbagbo has retreated further, encircling himself with hard-liners and refusing a call from President Obama.

Secretary of State Hillary Rodham Clinton said Thursday that Obama had warned Gbagbo of "consequences" if he does not step aside and peacefully transfer power to his successor.

State Department spokesman P.J. Crowley said unspecified sanctions could be applied to Gbagbo and to others "if he makes the wrong choice."