An American woman who has served the United Nations for 25 years has been locked in a bitter struggle with the organization's leadership for the past 18 months over sexual harassment allegations.

Cynthia Brzak (search) says she was sexually assaulted by Ruud Lubbers (search), the former U.N. High Commissioner for Refugees and a former Dutch prime minister, in 2003 as she left a meeting at UNHCR headquarters in Geneva.

Brzak, who has never spoken publicly about the incident, gave FOX News an exclusive interview.

"He puts a hand on either side of my waist, grabs me, pulls me back, steps up and holds me for about five seconds ... with his groin pushed into the back of me," Brzak said.

Click in the video box to the right for a complete report by FOX News' Jonathan Hunt.

The U.N.'s Office of Internal Oversight Services investigated and backed Brzak's complaint, saying, in June 2004, "... the allegation against Mr. Lubbers is substantiated." It added that, "... new allegations ... were also examined and indicate a pattern of sexual harassment by Mr. Lubbers."

But Brzak says U.N. Secretary-General Kofi Annan (search) refused to take action on the matter.

"The United Nations has nothing going for it but principles and honor," she said. "We go into countries with our principles and our honor, and we say to governments, 'you shouldn't do this, you should do that better,' that's all we've got. And he just ripped it all to shreds publicly."

Lubbers was eventually forced to resign, but he said the allegations were "made up" and nothing more than "slander." Only last week, Annan said in Geneva that Lubbers had resigned not because he was guilty of sexual harrassment, but because the media made such a big issue of it.

Brzak said that when she hears the secretary-general say that, she thinks: "The man is a liar ... the secretary-general is a liar. That's pretty serious."

Brzak now has been told that her job at the U.N. has been targeted for cuts, according to e-mails obtained by FOX News. She believes that's in retaliation for the stand she's taken. She says one word from Annan could save her job, but she has yet to hear from him.

When FOX News brought the matter up with the secretary's general's office on Tuesday, Annan's spokesman said Brzak's job is not at risk, "not now, not ever."