In a statement, Minority Leader Nancy Pelosi said she found the young woman's documented account, reported by BuzzFeed News, to be convincing. The woman, identified only as Samantha, said Kihuen propositioned her for dates and sex despite her repeated rejections.
On two occasions, she said, he touched her thighs without consent.
"In light of these upsetting allegations, Congressman Kihuen should resign," Pelosi said.
The California lawmaker said she spoke to the 37-year-old congressman Friday night.
The request comes hours after Rep. Ben Ray Lujan, chairman of the Democratic Congressional Campaign Committee, also had pressed for Kihuen's resignation, saying House members and candidates should be held to the highest standard, and anyone guilty of sexual harassment or assault should not hold elected office.
Kihuen said in a statement that he did not remember the incidents with the aide, who worked as his campaign finance director and was a valued member of his team.
"I sincerely apologize for anything that I may have said or done that made her feel uncomfortable. I take this matter seriously as it is not indicative of who I am," Kihuen said. "But I want to make it clear that I don't recall any of the circumstances she described."
BuzzFeed withheld her last name at her request.
Kihuen gave no indication in the statement that he would follow Lujan's admonition.
"I have spent my fifteen years in public service fighting for women's equality, and I will continue to do so," the congressman said.
Sen. Catherine Cortez Masto, D-Nev., called for a "full, fair and expedient investigation against Congressman Kihuen and any other member of Congress who have women or men come forward with allegations of inappropriate behavior."
"This process must be open, transparent and have an appropriate investigatory timeline that delivers justice," she said.
Congressional leaders are under pressure to respond to a national outcry against sexual harassment. The allegations against Kihuen come after Rep. John Conyers, D-Mich., was accused of sexually harassing members of his staff and Sen. Al Franken, D-Minn., was accused of inappropriate touching.
Pelosi has called on Conyers to resign. His lawyer, Arnold Reed, said Friday the congressman, the longest-serving member of the House, will discuss in the next few days whether to resign, but his health will be the paramount factor and not pressure from Washington politicians.
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