BOISE, Idaho (Reuters) - Republican Sen. Larry Craig of Idaho, caught in a sex scandal that quickly lost him the support of his party after his arrest in a men's toilet, said on Saturday he would resign from the U.S. Senate.
Craig pleaded guilty to disorderly conduct last month after he was arrested in an undercover investigation of lewd behavior in an airport men's room.
"To Idahoans I represent, to my staff, to my Senate colleagues, but most importantly to my wife and family, I apologize for what I have caused. I am deeply sorry," Craig, 62, said at a news conference.
The three-term senator from the solidly Republican and sparsely populated state said he would step down on September 30.
Craig's departure capped a week of turmoil for Republicans, already reeling from ethics problems, with the disclosure of his arrest.
Idaho Gov. C.L. "Butch" Otter will pick a successor to complete Craig's term, which runs through next year. He was expected to choose a Republican and maintain the current 51-49 Democratic control of the Senate.
Craig, who was elected to the Senate in 1990, is ending his career after the revelations on Monday of his guilty plea. He was arrested June 11 in the men's room at the Minneapolis-St. Paul airport, where police were targeting public sex.
According to a police report, Craig entered a toilet stall next to an undercover policeman and tapped his foot and waved his hand in gestures that the officer said signaled "a desire to engage in sexual conduct."
He was in the airport on the way to Washington that day.
Craig later said he regretted pleading guilty to the misdemeanor charge and claimed he did nothing wrong.
"I am not gay, I never have been gay," he said on Tuesday, with his wife at his side. They have three children.
President George W. Bush telephoned Craig shortly after the resignation announcement to say that he knew it was a difficult decision and the president wished the senator well, said White House spokesman Scott Stanzel.
Craig "made the right decision for himself, for his family, his constituents and the United States Senate," Stanzel said.
Craig had found himself denying allegations that he was homosexual from early on in his Washington career, which began in the House of Representatives in 1981.
At the same time, the conservative senator opposed gay rights and voted in favor of an amendment to the U.S. Constitution to define marriage as a union between one man and one woman.
On Saturday, Craig said he felt he should resign from the Senate to pursue legal options in the case.
"I have little control over what people choose to believe, but clearing my name is important to me and my family," he said.
Craig saw much of his party abandon him during the week as Republicans sought to distance themselves from the scandal.
Top Republicans called for a Senate Ethics Committee probe of his actions and asked Craig to step down temporarily from his committee assignments.
At the news conference, Craig thanked the handful of officials who appeared with him on the podium, adding, "For any public official at this moment in time to be standing with Larry Craig is in itself a humbling experience."
The Republican National Committee was on the verge of calling for Craig to resign on Friday and top Idaho Republicans also urged him to quit, a party aide said.
"He has been forced out, essentially," the aide said on condition of anonymity. "This is what we all want."
Democrats won control of Congress in last year's elections partly because of Republican scandals, including bribery and one lawmaker making unwanted advances on teenage Congressional interns.
Republicans have been battered by other scandals this year, including an investigation of Sen. Ted Stevens of Alaska, the longest-serving Republican in Senate history, and by Louisiana Sen. David Vitter's admission of a "serious sin" after he was linked to an escort service that police described as a prostitution ring.