ABIDJAN, Ivory Coast – The United States warned Laurent Gbagbo that he faces punitive sanctions if he continues to refuse to step down following a disputed election that the United Nations says were won by his opponent.

The African Union, meanwhile, suspended Ivory Coast's membership on 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 he rejected the results released by his country's electoral commission which showed that the opposition leader Alassane Ouattara had won by a nearly 10-point margin. Those results were certified by the United Nations who declared that Ouattara had won by "an irrefutable margin."

The country has been on a knife's edge ever since the results were released last week. The international community including the United States, the European Union, former colonizer France, the African Union and the United Nations have spoken in one voice telling Gbagbo to step aside.

Since then Gbagbo has retreated further and further, encircling himself with hard-liners and going so far as to refuse a telephone call from President Barack Obama.

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

The urbane 65-year-old who spent years as an expatriate in France is likely to face a travel ban that would target not only him but also his family, including his children and may prevent him from leaving the country. Among the only countries in Europe that has not spoken out against Gbagbo is Russia, prompting one senior diplomat to joke that Gbagbo may need to take his summer vacation in Moscow.

The official said that even the children of those in Gbagbo's entourage studying in the U.S. could be targeted by these measures and would be vulnerable to deportation. A senior advisor to Gbagbo confirmed that Gbagbo's stepdaughters — the children of the first lady — are believed to be living in Atlanta, Ga.

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

Ivory Coast is proving to be a test case for democracy in Africa because it is the only place where the U.N. was invited by the country itself to supervise the vote and certify the verdict following a 2005 peace accord. That puts this contested election in a different category than recent ones in Kenya and Zimbabwe, where the international community was unable to force sitting presidents to hand over power. In both of those instances, the candidate considered by most observers to be the race's legitimate winner were forced to accept power-sharing arrangements with the incumbent.