House Minority Leader Nancy Pelosi called Sunday for an ethics investigation of Rep. David Wu (D-Ore.) after allegations that the congressman engaged in an "unwanted sexual encounter" with a young woman.

Wu will not resign, but sources claim he will not seek reelection in 2012, The Oregonian reported.

"I call on the Ethics Committee to initiate an investigation into the allegations against Congressman Wu," Pelosi said in a statement Sunday.

"With deep disappointment and sadness about this situation, I hope that the Ethics Committee will take up this matter."

Democratic lawmakers met with Wu to pressure him to resign after the allegations first surfaced Friday, The Oregonian reported.

House Minority Leader Nancy Pelosi spoke with the congressman by phone Saturday night but would not comment on her discussion.

The Oregonian first reported Friday that Wu had been accused of having an "unwanted sexual encounter" with a young woman.

The woman called Wu's office and left a "distraught" voicemail message accusing Wu of "aggressive and unwanted sexual behavior," the Portland paper reported.

The woman is the daughter of a longtime friend and campaign donor, according to the report.

Wu gave a one-sentence response to The Oregonian: "This is very serious, and I have absolutely no desire to bring unwanted publicity, attention, or stress to a young woman and her family." 

Democratic Congressional Campaign Committee Chairman Steve Israel backed Pelosi's calls for an inquiry. Israel said the "new allegations of unacceptable behavior by Congressman Wu are extremely serious and disturbing. I strongly agree with Leader Pelosi’s request that the House Ethics Committee use its authority to begin an immediate investigation."

Wu made headlines for erratic behavior during his 2010 reelection campaign that led some of his staff to quit.

Wu sent staffers a picture of himself wearing a tiger Halloween costume and emails written in the voices of his children.

Wu won a seventh term in Congress in November, fending off a tough challenge from Republican Rob Cornilles.

In February Wu said that he'd sought medical help.

"Last October was not a good month. It was very stressful. I did some things, I said some things, which I sincerely regret now," he said on ABC's "Good Morning America."

—This story was originally posted on July 23 at 7:38 a.m. and has been updated.