BEIRUT, Lebanon — President Bashar al-Assad of Syria on Wednesday celebrated his overwhelming victory in a deeply disputed election, asserting his confidence and defiance in the Syrian conflict as supporters savored his success in thwarting the United States.

Syrian officials announced that Mr. Assad had been re-elected with 88.7 percent of the vote and reported turnout of 73.4 percent of eligible voters. Those numbers could be questioned on many levels, but that did not matter much, as the election was primarily a display of Mr. Assad’s continued control of important Syrian cities, the loyalty of his core supporters and the failures of his opposition and its backers.

For United States officials, it was a less triumphant day. Mr. Assad’s supporters celebrated with gunfire in Damascus and even in neighboring Lebanon, where Secretary of State John Kerry paid a visit on Wednesday. But the Americans were confronted with a sense that their policy on Syria and in the region was adrift.

The night before, Robert S. Ford, the career diplomat and Arabic speaker who was until recently the nominal ambassador to Syria and the main executor of American policy there, declared on “PBS NewsHour” that he quit his post in February because the policy had failed and he “could no longer defend” it in public. He said that with the United States unwilling to seriously aid potential allies in the Syrian opposition, Russia and Iran had been “driving” the war’s dynamics by hugely increasing their support for Mr. Assad.