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.

Before declaring Ouattara the winner, the U.N. reviewed results from all 20,000 polling stations. U.N. Special Representative Choi Young-jin said the results were clear-cut and gave Ouattara a decisive victory.

On Thursday, he arrived at the Golf Hotel and met behind closed doors with Ouattara, who has been forced to use the hotel as his headquarters because Gbagbo is still occupying the presidential palace.

The hotel has turned into a fortress, protected by sandbags, coils of barbed wire and U.N. armored personnel carriers amid rumors the military under Gbagbo's control was planning an assault.

Upon his departure, he told reporters that he is ready to meet Gbagbo, if Gbagbo is willing to talk. "I'm ready to pay him a visit," Choi said.

The African Union's Peace and Security Council suspended Ivory Coast's membership, saying it "strongly urges Mr. Laurent Gbagbo to respect the results of the election and to facilitate, without delay, the transfer of power to the President-elect, in the best interest of Cote d'Ivoire, the region and Africa as a whole.

Despite the increasing pressure, Gbagbo has appeared unflappable, going ahead with a rushed inauguration and later naming government ministers to his cabinet. He has banned foreign TV and radio, and citizens have been fed a 24-hour cycle of images showing him taking the oath of office and interviews with local constitutional experts explaining why Gbagbo is the legitimate president.

Once considered an African success story, Ivory Coast's economy was destroyed by a civil war that erupted in 2002. Gbagbo, who was president when the war broke out, failed to hold elections in 2005 when his term expired because armed rebels still controlled the northern half of the country.

The country remained in political deadlock, with repeated outbursts of fighting until 2007, when a deal was signed by all the parties paving the way for the election. But even then, he was reluctant to hold elections and the date for the ballot was scheduled and then canceled at least six times before it was finally held in October.

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Associated Press writer Marco Chown Oved contributed to this report.