Speaking at the United State of Women summit in Washington on Tuesday, Vice President Biden said that seven women he met on a rope line at a White House picnic Monday told him they had been raped.

Biden, who has made sexual violence a longstanding policy priority of his, cited that incident as an example of how assault survivors now feel empowered to talk about their experience in an effort to change U.S. culture more broadly.

"It’s critical to free the voices of survivors across the country, but most of all, let them know that we are listening," Biden said, adding that in the course of greeting administration staffers at the picnic, "seven young women pulled me close and said, 'Thank you, I’ve been raped. I didn’t think anybody listened.' Seven. Yesterday."

"The reason I tell the story, it’s not about me," the vice president said. "It’s about women getting to the point where they feel somebody [will] listen to them."

Biden was introduced by Megan Yap, a White House Champion of Change honoree who conducts research on how college and university campuses address sexual assault. Yap, who was raped as an undergraduate at the University of California San Diego, said she now works to ensure schools use trauma-informed research to craft their policies "so that survivors do not suffer any more than they already have."

"While I was powerless against the man who attacked me, I am not powerless in ending rape culture," she said, as the crowd at the Walter E. Washington Convention Center applauded. "I realized I could do something about it."

In a nearly hour-long address Biden spoke extensively about the need to hold rapists, the institutions where sexual misconduct occurs and bystanders to sexual assault more accountable. The vice president has led the administration's "It's On Us" effort, a public awareness campaign aimed at preventing sexual assault on college and university campuses by enlisting the support of men as well as women.

"This has literally been, not figuratively, the cause of my life," Biden said, adding that issues such as sexual violence and denying women and girls opportunities stems from a broader, systemic bias in our shared culture. "It’s ultimately about the abuse of power. It’s all about power."

Noting that he had been able to change both federal and state law on these issues -- including with the passage of the Violence Against Women Act, which was authorized in 1994 and reauthorized in 2013 -- Biden noted that these changes have been insufficient.

"I got it changed, but it didn’t change our culture," he said, referring to a Delaware law that carried a more serious charge for rape by a stranger than by an assailant whom the victim knew.

If a fraternity member sees someone else at a party taking a woman who is incapacitated upstairs, Biden said, "If you don’t have the courage to say, 'Hey Jack, not in my house,' you are an accomplice. You are an accomplice."

Biden predicted he would be "roundly criticized' for making those remarks.

The large audience at the convention center gave Biden, as well as the rest of the speakers at the event, an enthusiastic reception. The first-ever summit of its kind, the gathering aims to promote gender equality in the United States and abroad.

More than two dozen companies — including Airbnb, Amazon, American Airlines, Dow Chemical and Pepsico — agreed Tuesday to undertake a yearly company-wide gender pay analysis as part of the summit.

Tina Tchen, executive director for the White House Council on Women and Girls, said in an interview Monday that while “there’s been a continued sense of frustration at not getting a national paycheck fairness act,” the 28 firms’ adoption of the White House’s equal pay pledge shows that companies are willing to take steps ranging from reviewing their hiring and promotion processes to identifying other ways of ensuring that women and men in similar occupations are paid at comparable rates.

Tchen, who also serves as chief of staff to the first lady, said the inaugural event will examine what the administration has done so far and will also explore “what needs to be done.”

Other commitments include a tool kit that Harvard Law School’s Negotiation and Mediation Clinical Program will develop for community college students across the country, so women can become better prepared to negotiate for higher salaries when they enter the workforce, and a $15 million pledge by the nonprofit group CARE to help educate 3 million adolescent girls in six countries. Oracle pledged to spend $3 million worldwide to help girls learn in the fields of science, technology, engineering and math.

The federal government will also finalize a Labor Department rule Tuesday on what constitutes sex discrimination among federal contractors and subcontractors, the first update to the regulations since the 1970s. The rule addresses everything from pregnancy-related accommodations to prohibitions on discrimination based on a person’s gender identity.

“This is a rule that HR professionals will look at for their guidelines,” Tchen said, adding that while much of the rule reflects the latest case law on these topics, “when you look at what HR officers are reading, they’re not reading case law.”

The summit will draw more than 5,000 women to Washington, including Oprah Winfrey, who will participate in a conversation with Michelle Obama on Tuesday afternoon titled, “Trailblazing the Path for the Next Generation of Women.”

President Obama is also scheduled to speak more broadly about the push for gender equality.

Tchen said the White House allotted extra tickets to groups so that “a fairly strong contingent of young women” could attend along with more senior leaders of organizations.

And the youngest official participant of all is introducing the president: Mikaila Ulmer, the 11-year old founder of the company Me & the Bees Lemonade, based in Austin, Tex.

“Talk about the power that young people have,” Tchen said. “Her lemonade got picked up by Whole Foods Market.”