A conservative U.S. senator embroiled in an airport restroom sex scandal has seen his quarter-century national political career crumble from the pressure of the backlash.

Sen. Larry Craig, R-Idaho, told a news conference in Boise on Saturday that he would resign from the Senate at the end of September.

"I apologize for what I have caused," said Craig, his wife Suzanne and some of his children at his side. "I am deeply sorry."

Craig was arrested on June 11 at the Minneapolis-St. Paul airport by an undercover officer probing reports that homosexual activity was taking place in a bathroom at the airport.

Although he quietly pleaded guilty to a minor charge on Aug. 8, Craig denied he had tried to solicit sex from a male stranger, saying he has little control over what people choose to believe.

"Having said that, to pursue my legal options as I continue to serve Idaho would be an unwanted and unfair distraction of my job and for my senate colleagues," Craig said. "It is with sadness and deep regret that I announce that it is my intent to resign from the Senate effective Sept. 30."

Republic Gov. Jim Otter, who attended the news conference, will name a temporary replacement for Craig.

U.S. President George W. Bush called Craig after the announcement, said White House spokesman Scott Stanzel. Bush told Craig that he knew it had been a difficult decision to make.

"Senator Craig made the right decision for himself, for his family, his constituents and the United States Senate," Stanzel said.

Police claim Craig solicited an undercover officer for sex in the men's washroom at the airport, using a series of signals such as foot tapping and placing his hand under the partition between the stalls.

Craig pleaded guilty to a misconduct charge on Aug. 8. He was charged US$500 in fines and fees and was given a 10-day suspended sentence.

Craig maintains innocence

Craig has maintained that he is not gay and did nothing wrong during the airport encounter. His only error in judgment was entering a guilty plea in early August without first consulting a lawyer, he has said.

On Saturday, he said he has been moved by the "tremendous outpouring of support" he has received from "friends, family, staff and fellow Idahoans."

Boise resident Bayard Gregory sounded skeptical about Craig's protestations.

"It's a horribly embarrassing experience to go through," Gregory said. "But if it were me, and I had done nothing wrong, I wouldn't have pleaded guilty."

Though Craig has maintained a low profile since his statement on Tuesday, he reportedly spent much time gauging support. Craig found little from his fellow Republican politicians.

Republican legislators removed Craig from his leadership responsibilities and ordered an ethics committee investigation into his actions soon after it became public knowledge on Monday.

Senate Minority Leader Mitch McConnell (R-Ky.), who had been one of Craig's fiercest critics on this issue, said Saturday that Craig "made a difficult decision, but the right one.

"It is my hope he will be remembered not for this, but for his three decades of dedicated public service," he said.

Craig had consistently voted against bills that would advance gay rights. The conservative rancher opposes gay marriage.

Republican strategist Rich Galen told CTV Newsnet that Craig has lost all credibility.

"The confidence in him has been lost by his colleagues in the Senate," Galen said.

Galen said the impact on the Republican Party in Idaho, however, will be minimal. He said the state is overwhelmingly Republican in its support, and voters are unlikely to see the scandal as a reflection on the party as a whole.

Partisan U.S. Democrats might take some satisfaction from the fact that Craig helped lead the charge against President Bill Clinton over the Monica Lewinsky affair almost a decade ago. Clinton received oral sex from Lewinsky, an intern, in the White House.

"It's a bad boy, Bill Clinton. You're a naughty boy," Craig said in a Meet The Press appearance at the  time.

With a report from CTV's Jed Kahane and files from The Associated Press