Yet Abdullah seemed to be keeping his options open until the last second, as he has done through the Afghan political crisis. Those close to him, speaking on condition of anonymity on Saturday, said he was still trying to decide whether to publicly denounce Karzai, whom he has accused of stealing the Aug. 20 election, or to step down without a fight.

American and other Western diplomatic officials said late Saturday that they were worried that a defiant statement by  Abdullah could lead to violence and undermine the credibility of Karzai, and they were urging him to bow out gracefully. Obama administration officials have scrambled for weeks to end the deadlock, trying to ensure a credible government as President Obama weighs whether to increase the American military presence in Afghanistan.