The Trump administration’s antitrust chief said Friday he's unsettled by allegations that the biggest U.S. technology companies are suppressing conservative voices on their platforms.

Whether the bias claimed by Republicans – which companies from Facebook to Google and Twitter have denied – is harmful "depends on what kind of bias we are talking about," Assistant Attorney General Makan Delrahim said at a Friday morning event organized by news outlet Axios. "I’m concerned about the concerns that have been raised."

Delrahim's comments came the same day that Google’s chief executive officer is slated to meet with top Republicans, who are likely to question him about whether the company's marquee search engine discriminates against conservative websites as well as its expansion plans in China.

While President Trump is reportedly pushing a plan to open antitrust reviews of companies like Google and social media giant Facebook, Delrahim avoided saying what the Department of Justice would do. He did warn, however, that the federal government is closely scrutinizing the behavior of such firms for possible anti-competitive actions.

There are "very valid concerns," he said, about whether the businesses are growing so large that they "are stifling innovation and consumer choice."

Delrahim confirmed that the agency has heard anecdotes about technology firms taking steps to block new entrants into the industry, though "I don’t know if any of the enforcement bodies necessarily have that credible evidence."

There isn’t a question of whether some companies have significant market power, Delrahim noted, but whether “they are taking action that harms a new entrant’s ability.”

After assuming the top antitrust post, Delrahim launched a review of a pending merger between AT&T and Time Warner. The transaction, which was eventually challenged in court, was allowed to proceed after a federal judge ruled in favor of the companies. The Justice Department is appealing the decision.

Asked about AT&T’s plan to invest heavily in HBO, Delrahim called it a “great idea” and labeled the cable network an “incredible product.”

AT&T Chief Executive Officer Randall Stephenson recently described HBO as the “Tiffany” of streaming, referring to the popular top-end jewelry chain, while labeling rival Netflix as Walmart.