The Obama administration Tuesday joined a push to increase diversity in the tech sector, announcing commitments by an array of venture capital investors and Silicon Valley firms to hire and promote more women and minorities.

In the announcement, to be made during the White House's first Demo Day for startups, 40 venture capital firms including Andreessen Horowitz and Kleiner Perkins promised to focus on funding startups led by female and minority founders. Companies such as Intel, Box, and Pinterest committed to a battery of programs including mandatory interviews of minorities in recruiting as well as partnerships with universities to improve the pipeline for talent.

The efforts, the most comprehensive from the tech sector yet, come amid a growing concern that the most vibrant sector of the economy is largely leaving out women and minority workers and leaders. But even with the White House's support, it will be difficult to significantly change the embarrassing paucity of diversity without more explicit and stronger commitments by companies and venture firms, civil rights groups and political leaders say.

Scrutiny over Silicon Valley's lack of diversity has intensified with dismal reports on the state of minority hiring by leading companies such as Facebook, Yahoo, and others. In particular, the percentage of blacks and Hispanics significantly lag the number of those minorities obtaining engineering degrees from universities or their representation in the overall labor force. And those numbers haven't improved in recent years. Yahoo said last month that African Americans comprised 2 percent of its workers, while Hispanics were at 4 percent. Facebook said last month that it had employed just 81 blacks among its 5,500 U.S. workers in 2014.

Some at these companies say that "unconscious biases" can lead white men who dominate the venture capital world to hire largely among their own social, business and school networks. And several companies, such as Box, Indiegogo and DropBox, said they will train their staff to be more aware of such issues.

IBM said it would expand its relationship with the group Girls Who Code. Facebook and Microsoft say they are focusing on expanding diversity in its vast ecosystem of corporate partners. Amazon announced plans to change their screening of engineering recruits to lessen potential biases.

And some studies have shown diversity leads to higher financial returns.

"Not only is it the right thing to do, it's highly profitable to have a diverse team," said Obama's top tech aide U.S. Chief Technology Officer Megan Smith.

But some civil rights advocates say the most effective efforts are to set clear targets for hiring and to invest heavily in funding startups expressly run by minorities.

"The thrust of the problem is systemic institutional racism. Unconscious bias tends to reduce the problem to a personal level, which is not the right way to look at this," said Butch Wing, the head of Silicon Valley civil rights efforts for the Rainbow PUSH Coalition.

Some tech companies said they would do more than just train workers. This week, Intel said it would double its recruitment referral bonus of women, minority and veteran job candidates and has set a goal of making its workforce reflect the demographics of the overall labor force in five years. The company  has also committed $250 million in funding of minority-run startups.

Last week, Pinterest set specific targets for minority hiring in 2016. It said it would strive for women to represent 30 percent of all new full-time engineers and for minorities to make up at least 8 percent of those new recruits.

"We think one reason it’s been so hard to get numbers to change is that companies haven’t stated specific goals," said Pinterest CEO Evan Sharp in a blog post.