WASHINGTON — Oregon Democratic Rep. David Wu faced increased pressure Monday after House Democratic leader Nancy Pelosi called for an ethics investigation over an 18-year-old woman's claim of an "unwanted sexual encounter" with him.

Pelosi issued a statement Sunday night calling on the House Ethics Committee to begin looking into the allegations against Wu.

Meanwhile, lawmakers will find it harder to avoid questions about their position on Wu's future, a scenario similar to six weeks ago when they had to deal with the distraction of former Democratic Rep. Anthony Weiner, who had sent lewd photos of himself to women online. Unlike the media frenzy that ensued in the Weiner case, Wu's situation has prompted little attention so far because of the intense focus on lawmakers' struggle to reach a deal on raising the national debt ceiling.

Wu and Pelosi had a telephone conversation Saturday but neither politician has disclosed details.

Wu hasn't spoken publicly about Pelosi's statement.

The Oregonian, citing an unidentified senior Democrat official, said that Wu did not intend to resign but would complete his term and retire in 2012.

Wu would have faced an extremely difficult primary challenge, likely the most difficult of his career. One of the candidates challenging Wu in next year's primary, state Labor Commissioner Brad Avakian, said Wu should see Pelosi's calls for an ethics investigation as a signal to step down immediately.

"An ethics investigation would result in a long drawn-out distraction and prolong the public pain" for the unidentified woman who has accused Wu, Avakian spokesman Jake Weigler said. "For the sake of our community and this young woman and her family, as well as his own family, David Wu should do the right thing and step aside now."

Another Wu challenger in the Democratic primary, state Rep. Brat Witt, said an ethics investigation is needed so "we get to the bottom of the allegations and determine what the facts are."

Wu's only response so far has been a brief statement late Friday: "This is very serious, and I have absolutely no desire to bring unwanted publicity, attention or stress to a young woman and her family."

Oregon Democrats have been waiting for word on how Wu plans to respond further to the allegation and the resignation demands.

Spokesmen for both Gov. John Kitzhaber and the state party said Wu hadn't reached out to top Democrats in Oregon.

"At this point, I don't believe those conversations have happened," said Trent Lutz, executive director of the state party.

Lutz and other party members said they hoped Wu would respond directly to the allegation reported by the Oregonian newspaper. The paper quoted sources who said a young woman left voicemail at Wu's Portland office earlier this year accusing him of an unwanted sexual encounter three weeks after last year's election.

Citing anonymous sources, The Oregonian reported that Wu told senior aides that the sexual encounter with the young woman in California was consensual. The paper reported Facebook notes indicate she graduated from high school in 2010 and that she registered to vote in California last August.

The paper said the woman decided not to press changes because there were no witnesses and it would have been her word against Wu's.

The newspaper said its information came from multiple sources familiar with the allegation.

In Wu's district stretching from downtown Portland to the Pacific Ocean in northwest Oregon, county-level leaders said they, too, were hoping for more from Wu.

"I'm waiting for more details to come out," said Cris Land, party chair in Columbia County.

The heart of the 1st Congressional District is Washington County, a center of high tech and suburban development and the home of David Robinson, a former Navy officer and municipal official who lost by a margin of 4-1 to Wu in the Democratic primary last year.

Robinson said he will ask fellow activists in Washington County on Wednesday to approve a vote of no confidence in Wu, calling the woman's allegation "just another in a long line of disappointments and improprieties."

Wu has won seven terms. In 2004, he won despite acknowledging a decades-old college incident in which he tried to force a former girlfriend to have sex. Voters said they disliked an opponent's attempt to use that against Wu.

In January this year, seven staffers resigned because of behavior that included sending a photo of himself in a tiger costume to a staff member and an angry public speech. Wu attributed those to a period of mental health challenges that began in 2008 as marital issues led to separation from his wife.

Associated Press writers Terrence Petty and Nigel Duara in Portland, Ore., contributed to this report. Tim Fought reported from Portland, Ore.