WASHINGTON — The younger brother of Republican presidential candidate John McCain has withdrawn from campaign activities and apologized for swearing at an emergency dispatcher after he called 911 to inquire about a traffic jam on the Woodrow Wilson Bridge.

Joe McCain, 66, said he was stepping aside to avoid becoming a liability for the Arizona senator before the Nov. 4 election. In an interview yesterday, he described the 911 call as "the biggest mistake I will ever make in my life, at least in politics," and said he thought he had hung up the phone before uttering an expletive.

The apology marked the second this month for him. He also apologized after referring to suburban Alexandria and Arlington County, Va., as "communist country" at a rally in suburban Loudoun County.

Asked about the expletive recorded in the 911 incident, he said: "... The truth is, I had no idea there was anybody on the other end of the phone."

It was early Tuesday when Joe McCain, en route to his home in Alexandria from campaign events in Scranton, Pa., approached the span in his Toyota Camry. He encountered a red light as he pulled up to the bridge, but traffic was flowing freely in the other direction.

Joe McCain said he flipped his radio to WTOP, where he learned that a test on the bridge was to blame for the stopped traffic. After about 40 minutes, he called 911.

"911. State your emergency," the dispatcher said, according to an audio clip.

"It's not an emergency. But do you know why on one side at the damn drawbridge of 95 traffic is stopped for 15 minutes and yet traffic's coming the other way?" McCain said.

"Sir, are you calling 911 to complain about traffic?" the operator asked.

"(Expletive) you," McCain said, hanging up the phone.

The dispatcher then called back and was sent to his voice mail, which enabled authorities to identify the caller.

Campaign spokesman Tucker Bounds said in an e-mail: "Joe recognizes his mistake and has apologized. We are moving on."

McCain said that at the time, he did not realize the "inappropriateness" of calling 911 about a traffic problem. He said he now recognizes it was a mistake.

He apologized for the 911 incident Friday in an interview with WTOP and said he has mailed a letter of apology to the dispatch center in Alexandria that handled the call.