By Asa Fitch

Microsoft Corp. won't sell facial-recognition technology to U.S. police until there is a national law regulating its use, the company's President Brad Smith said Thursday.

Microsoft joined other big tech names including Amazon.com Inc. and International Business Machines Corp. to call for clearer rules around the surveillance technology amid widespread concern about its potential for racial bias.

The issue has attracted greater attention amid growing outcry about police brutality and what many see as institutionalized racism in law-enforcement bodies sparked by the killing of George Floyd, a black man, in police custody.

Microsoft has long taken a careful stance on facial recognition, putting self-imposed curbs on its sales of the technology to law enforcement. As a result of those limits, Mr. Smith said during a Washington Post event that the company wasn't currently selling facial recognition to police in the U.S.

"We've decided that we will not sell facial recognition technology to police departments in the United States until we have a national law in place, grounded in human rights, that will govern this technology," he said.

Mr. Smith said last year that Microsoft had declined to sell facial recognition to a police department in California over concern that it could be used for mass surveillance. But the decision not to deal with police forces until laws are in place to regulate facial recognition took its caution a step further.

A wave of tech companies have been re-examining police use of their facial-recognition technology, which studies have shown can come with embedded racial and gender biases. Those biases mean people with darker skin and women tend to be misidentified more often than Caucasians and men.

Amazon on Wednesday placed a one-year moratorium on the use of its facial-recognition software by police. IBM said this week it exited the business.

Legislative curbs on facial recognition are at an early stage. While some cities, including the tech hub of San Francisco, have banned facial recognition's use by police, there are no similar federal-level curbs on its use. A bill introduced earlier this week in the House would prohibit real-time facial recognition in federal law-enforcement body cameras.

Write to Asa Fitch at asa.fitch@wsj.com