Congressman Gary Condit has acknowledged he had a five-month relationship with missing US government intern Chandra Levy.
But he said he had no idea what happened to her when she disappeared nearly four months ago.
In his first broadcast interview since the disappearance, the politician told ABC TV's Connie Chung that he has co-operated fully with police and did nothing to slow down the investigation.
"No one in Washington has been more co-operative than myself," Chung quoted Mr Condit as saying during the half-hour interview at a ranch in Modesto, owned by a friend of the member of the House of Representatives.
Mr Condit, 53 and married, described his relationship with the Levy as "close" but would not say whether they had a sexual relationship.
The 24-year-old Ms Levy, from Mr Condit's home district in Modesto, was in Washington for an internship at the US Bureau of Prisons.
Chung said Mr Condit related details of his final phone conversation with Ms Levy, which occurred several days before her disappearance on May 1. They talked about her travel plans to California and Mr Condit said she did not seem upset, Chung said.
Ms Levy was last seen on April 30 at a health club near her Washington apartment. Police have interviewed Mr Condit four times, but have said repeatedly he is not a suspect and that they have no idea what happened to her.
Mr Condit, a California Democrat, has been criticised by some of his congressional colleagues and constituents for not publicly telling all he knows about Ms Levy. Three newspapers serving his district have called for his resignation.
A series of interviews that began on Tuesday are meant to rebuild the reputation of the seven-term congressman. The ABC interview, offering the combination of political scandal and the tragedy of a missing woman, is expected to be one of the most-watched programmes of the summer.