Mr. Strauss-Kahn, 62, who was widely expected to become the Socialist candidate for the French presidency, was apprehended by detectives of the Port Authority of New York and New Jersey in the first-class section of the jetliner, and immediately turned over to detectives from the Midtown South Precinct, officials said.
The New York Police Department arrested Mr. Strauss-Kahn at 2:15 a.m. Sunday “on charges of criminal sexual act, attempted rape, and an unlawful imprisonment in connection with a sexual assault on a 32-year-old chambermaid in the luxury suite of a Midtown Manhattan hotel yesterday” about 1 p.m., Deputy Commissioner Paul J. Browne, the department’s chief spokesman, said.
Reached by telephone, Benjamin Brafman, a lawyer, said he would be representing Mr. Strauss-Kahn with William Taylor, a lawyer in Washington.
“We have not yet been able to meet with our client and we may have more to say tomorrow,” said Mr. Brafman, who said he had been contacted late Saturday night. He said Mr. Strauss-Kahn was being housed at the police department’s Special Victims Unit.
Early Sunday morning, Mr. Brafman said that his client “will plead not guilty.”
Mr. Strauss-Kahn, a former French finance minister, had been expected to declare his candidacy soon, after three and a half years as the leader of the fund, which is based in Washington. He was considered by many to have done a good job in a period of intense global economic strain, when the institution itself had become vital to the smooth running of the world and the European economy.
His apprehension came at about 4:40 p.m., when two detectives of the Port Authority suddenly boarded Air France Flight 23, as the plane idled at the departure gate, said John P. L. Kelly, a spokesman for the agency.
“It was 10 minutes before its scheduled departure,” Mr. Kelly said. “They were just about to close the doors.”
Mr. Kelly said that Mr. Strauss-Kahn was traveling alone and that he was not handcuffed during the apprehension.
“He complied with the detectives’ directions,” Mr. Kelly said.
The Port Authority officers were acting on information from the Police Department, whose detectives had been investigating the assault of a female employee of Sofitel New York, at 45 West 44th Street, near Times Square. Working quickly, the city detectives learned he had boarded a flight at Kennedy Airport to leave the country.
Though Mr. Strauss-Kahn received generally high marks for his stewardship of the fund, his reputation was tarnished in 2008 by an affair with a Hungarian economist who was a subordinate there. The fund decided to stand by him despite concluding that he had shown poor judgment in the affair. Mr. Strauss-Kahn issued an apology to I.M.F. employees and to his wife, Anne Sinclair, an American-born French journalist.
In his statement then, Mr. Strauss-Kahn said, “I am grateful that the board has confirmed that there was no abuse of authority on my part, but I accept that this incident represents a serious error of judgment.” The economist, Piroska Nagy, left the fund as part of a buyout of nearly 600 employees instituted by Mr. Strauss-Kahn to cut costs.
In the New York case, Mr. Browne said that it was about 1 p.m. on Saturday when the maid, a 32-year-old woman, entered Mr. Strauss-Kahn’s suite — Room 2806 — believing it was unoccupied. Mr. Browne said that the suite, which cost $3,000 a night, had a foyer, a conference room, a living room and a bedroom, and that Mr. Strauss-Khan had checked in on Friday.
As she was in the foyer, “he came out of the bathroom, fully naked, and attempted to sexually assault her,” Mr. Browne said, adding, “He grabs her, according to her account, and pulls her into the bedroom and onto the bed.” He locked the door to the suite, Mr. Browne said.
“She fights him off, and he then drags her down the hallway to the bathroom, where he sexually assaults her a second time,” Mr. Browne added.
At some point during the assault, the woman broke free, Mr. Browne said, and “she fled, reported it to other hotel personnel, who called 911.” He added, “When the police arrived, he was not there.” Mr. Browne said Mr. Strauss-Kahn appeared to have left in a hurry. In the room, investigators found his cell phone, which he had left behind, and one law enforcement official said that the investigation uncovered forensic evidence that would contain DNA.
Mr. Browne added, “We learned that he was on an Air France plane,” and the plane was held at the gate, where Mr. Strauss-Kahn was taken into custody. Later Saturday night, Mr. Browne said Mr. Strauss-Kahn was in a police holding cell.
Mr. Browne said the city’s Emergency Medical Service took the maid to Roosevelt Hospital for what Mr. Browne described as treatment for “minor injuries.”
No matter the outcome of Saturday’s episode, it will most likely throw the French political world into turmoil and the Socialist Party into an embarrassing confusion.
Mr. Strauss-Kahn, a leading member of the party, has been considered the front-runner for the next presidential election in France in May 2012. Opinion polls have shown him to be the Socialists’ most popular candidate and running well ahead of the incumbent, Nicolas Sarkozy, who leads the center-right party.
France has been waiting for Mr. Strauss-Kahn to decide whether to run for his party’s nomination in a series of primaries, which would mean giving up his post at the fund.
The view in France was that if Mr. Strauss-Kahn wanted to run, he would have to make his intentions clear early this summer, and most politicians and analysts have been predicting that he would not be able to resist the chance to run the country.
Mr. Strauss-Kahn contested for the nomination five years ago, losing to Ségolène Royal, who ultimately lost a second-round runoff to Mr. Sarkozy. Mr. Sarkozy then arranged for Mr. Strauss-Kahn to get the I.M.F. job, partly to remove a popular rival from France’s political landscape.
Mr. Strauss-Kahn was the French minister of economy under the Socialist Prime Minister Lionel Jospin, from 1997 to 1999, and he has also been a professor of economics at the Paris Institute of Political Studies.
In 1995, he was elected mayor of Sarcelles, a poor suburb of Paris, and married Ms. Sinclair.
The couple is known to enjoy the finer things in life, and Mr. Strauss-Kahn has sometimes been attacked for being“caviar leftist.”
Recently Mr. Strauss-Kahn and his wife were photographed entering an expensive Porsche in Paris belonging to one of their friends. The image of a Socialist with Porsche tastes was quickly picked up by the news media, especially the newspapers that generally support Mr. Sarkozy.
William K. Rashbaum and Colin Moynihan contributed reporting. Story Reprinted from the New York Times.