Top black lawmakers are paying a visit to Airbnb, Apple, Twitter and other tech giants this week, as they continue their crusade to improve Silicon Valley’s hiring practices and train a new generation of diverse engineers and entrepreneurs.

For members of the Congressional Black Caucus, who arrived in the Bay Area on Monday, the tech sector has been too slow to diversify its executive ranks, invest in minority-owned start-ups and assist workers who can’t find jobs in tech hubs, like San Francisco, or afford those cities’ sky-high costs of living.

In response, lawmakers said they plan to raise those issues directly with tech companies on their home turf, hoping their political firepower — and subtle threats of bad press and tough regulation — might nudge some of the industry’s biggest players to be more mindful of black workers’ needs.

“We’re letting companies know they must provide greater opportunity to African Americans,” said Rep. G.K. Butterfield (D-N.C.) in an interview, adding they would “expose any company that provides lip service.”

A key, early goal of the visit: Butterfield said he and three fellow CBC members plan to ask tech executives to attend a public “summit” focused on diversity. Facebook CEO Mark Zuckerberg previously signaled he might attend such a gathering during his first-ever testimony to Congress in April — a hearing that focused on privacy yet at times pivoted to the company’s hiring practices. Facebook declined to comment Monday.

Already, CBC lawmakers said they had secured participation from PayPal, one of the firms they visited Monday. The company’s chief executive, Dan Schulman, said in a statement that PayPal is “fully committed to achieving a more diverse and inclusive workplace.”

The trip marks the third time the CBC has taken its message about diversity directly to the country’s tech capital since lawmakers announced their campaign in 2015. Since then, the 49-member bloc of black members of Congress has secured changes to tech companies’ business practices. Last year, for example, the CBC secured a commitment from Facebook that it would appoint a black board member, which the company ultimately announced in January. And it pushed Airbnb in 2016 to address accusations that hosts on the site were discriminating against African American renters. The home-sharing site did not immediately respond to a request for comment.

Despite its prodding, however, even the CBC has acknowledged that Facebook, Google and their tech peers continue to struggle to hire and retain black workers and leaders.

At Apple, which the CBC visited Monday, about 9 percent of its U.S. workforce is black while 54 percent of it is white, according to its most recent employment report. Still, the iPhone maker has said roughly half of its new hires between July 2016 and July 2017 came from “historically underrepresented groups in tech,” including women and people of color.

At Twitter, meanwhile, black employees make up 3.4 percent of its U.S. team while more than 43 percent is white, according to data it published in 2018. The company — along with its social media peers, such as Facebook — long has struggled to stop the spread of racist, extremist content on its platform. Twitter declined to comment for this story.

“The pace is change is much too slow,” said Rep. Barbara Lee, a Democratic congresswoman who represents a district not far from the Valley, during an interview. Among her constituents, she said she knows “many, many cases of African Americans who wanted to break into the workforce here … and never were able to do that.”

Along with hiring, Butterfield, Lee and their CBC colleagues said they would also press companies like Apple and Twitter this week to commit to new investment goals, including greater funding for science and engineering education programs. Lee said she would further urge executives this week to address the “unfortunate displacement of people who have historically lived” in the Bay Area, given the skyrocketing costs of living — fueled by a tech boom that’s helped some, but not all.

The plan is to “make sure these tech companies make a commitment to ensuring they are part of the solution and not part of the displacement process,” she explained.

To that end, Lee and her peers seem especially mindful of a company they are not planning to visit on their trip west this week: Amazon.com. The e-commerce giant is in the hunt for a locale to host its second headquarters — an office that could employ as many as 50,000 new workers. And the eventual arrival of the “HQ2″ could affect housing and rents, education and transportation, and the very character of the city that Amazon selects — so Lee said it would be critical for the company to keep diversity in mind.

“I have talked to members [of Congress] where the siting is being considered … to try to mitigate what has happened in the Bay Area,” she said. “I think that any company that is willing to set up new offices, new buildings, new operations, has to take into consideration the communities where they’re [looking].”

A spokeswoman for Amazon declined to comment. Amazon founder and chief executive Jeffrey P. Bezos owns The Washington Post.

Broadly, though, lawmakers insisted Monday that they don’t plan to ease the political pressure — a sign that even tougher scrutiny could follow if Democrats win a majority in the House or Senate, elevating some CBC members to key positions of power on Capitol Hill.

“We’re just going to tell the companies that the CBC is expecting better results, and if you want to work with us, then we want to work with you,” Butterfield said. “It’s good business to have a good relationship with a significant bloc of lawmakers.”