The CEOs of Amazon, Apple, Google and Facebook have all agreed to take part in a House Judiciary hearing on antitrust this month, Democratic lawmakers said Wednesday.

The hearing, potentially a landmark moment in the regulatory battle between Washington and Silicon Valley, would be held in late July and would mark the first time that the heads of America’s big four tech firms had testified together before Congress.

The House Judiciary antitrust subcommittee, which is chaired by David Cicilline, D-R.I., has been conducting an investigation into the big four tech firms, reviewing whether their market power poses a threat to competition and harms consumers.

Representatives from Facebook, Google and Amazon had told House lawmakers last month that their CEOs would be willing to testify as part of the antitrust probe — on the condition that all four chief executives were present.

Apple did not signal that its chief executive, Tim Cook, would be willing to testify, and the company has so far refused to comment on the matter.

On Wednesday, Rep. Cicilline told New York Times opinion columnist Kara Swisher that all four CEOs had agreed to testify at the hearing. NBC News confirmed that news with the office of Rep. Jerry Nadler (D-N.Y.).

Representatives for Apple did not comment.

A precise date for the hearing has not been given yet. Given the coronavirus pandemic, the hearing would almost certainly take place virtually, with the four CEOs appearing from home on split screen.