Ruud Lubbers, the U.N. high commissioner for refugees, acknowledged on Tuesday that he is the target of an internal U.N. investigation into an allegation of sexual harassment.

The probe stems from a formal complaint filed by a female U.N. staff member that the former Dutch prime minister harassed her at a U.N. meeting in December. Lubbers, 65, issued a statement in which he denied the charges, saying "there was no improper behavior on my part."

Lubbers said that the woman, whose name has not been released, filed the complaint on April 27, more than four months after the alleged incident at a Dec. 18 meeting in Geneva. Lubbers said five other U.N. staff members were present at the meeting.

The revelations, which were first reported by the New York Times, came as Lubbers arrived in Washington for a meeting with Secretary of State Colin L. Powell. The visit was intended to draw awareness to the refugee crises in Chad, Sudan and other trouble spots that have been overshadowed by the war in Iraq.

Lubbers referred to the sexual harassment charges in prepared remarks at the start of a news conference at the National Press Club, but he declined to respond to questions on the matter. Instead, Lubbers provided an overview of his recent visits to refugee camps in Iran, Afghanistan and Chad -- where more than 120,000 Sudanese have sought refuge from a government-backed campaign to depopulate Sudan's Darfur province.

He charged that the U.S.-led wars against Iraq and al Qaeda have heightened the threat to the United Nations' humanitarian relief workers around the world. He blamed President Bush for widening the rift between the West and the Muslim world in his quest to battle terrorism.

"Terrorism and al Qaeda, in particular, are real problems. But we must avoid becoming paralyzed by this monster," Lubbers said. "We've been damaged by the 'axis of evil' -- this Manichean vision of the world as split between the 'good' and the 'evil.' Unfortunately, like others we are paying the price for this."

Asked by a reporter if his message has been overshadowed by the harassment charge, he said that he did not believe it has.

U.N. official Ruud Lubbers denies the allegations.