A pair of top Trump administration antitrust enforcers on Tuesday acknowledged friction between their agencies amid a sweeping investigation into the giants of the tech industry, conceding that turf battles have played out over which companies from each side will probe for any anticompetitive conduct.

Appearing together before a panel of the Senate Judiciary Committee, the leader of the Justice Department's antitrust division and Joseph Simons, chairman of the Federal Trade Commission, testified that a longstanding power-sharing agreement has been strained as the two agencies hash out how to divide up investigations of companies including Facebook Inc. and Alphabet Inc.'s Google, along with Apple and Amazon.

"I cannot deny that there are instances where Chairman Simons' and my time is wasted on those types of squabbles," said Assistant Attorney General Makan Delrahim, who has headed the antitrust division since 2017.

The testimony came a day after the Wall Street Journal reported that Simons had sent the Justice Department a letter raising concerns about recent interactions between the two agencies. Simons, a former leading antitrust partner at Paul, Weiss, Rifkind, Wharton & Garrison, has led the FTC since May 2018. Delrahim was formerly a Brownstein Hyatt Farber Schreck partner.

This year, as the two agencies began their Big Tech investigation, they hashed out an agreement in which the Justice Department would pursue Google and Apple, and the FTC would take on Facebook and Amazon. In recent weeks, however, questions have emerged over whether the Justice Department has encroached on the FTC, specifically with regard to Facebook. The companies generally have asserted their practices are not anti-competitive.

On Tuesday, Sen. Mike Lee, R-Utah, appeared to play the role of mediator. At the outset of the hearing, Lee, chairman of the antitrust subcommittee, asked whether the power-sharing agreement between the FTC and Justice Department had broken down.

"For the vast majority of matters, we continue to operate under the existing clearance agreement," Simons said.

"I'll take that as a yes, things have broken down, at least in part," Lee replied.

"Yeah, I would agree with that," Simons replied.

Lee, who has raised concerns about clashes between the FTC and Justice Department, openly pondered whether two agencies should—at all—share antitrust enforcement authority. The Utah Republican asked Simons and Delrahim whether they would follow the U.S. model if they were standing up an antitrust regime in a foreign country.

"No, I wouldn't," Simons said.

Said Delrahim: "It's not the best model of efficiency."

The rift between the two agency leaders came months after the Justice Department undercut the FTC in the commission's antitrust case against the chip maker Qualcomm Inc.

In a California federal trial court, the FTC won a ruling that called for Qualcomm to make significant changes to its business practices. The Justice Department supported Qualcomm's appeal, arguing that the trial judge's ruling was incorrect and that the decision would inhibit 5G innovation. The U.S. Court of Appeals for the Ninth Circuit cited the Justice Department's argument when it stayed the judge's ruling last month, granting a reprieve to Qualcomm.

At the close of Tuesday's hearing, Lee launched into a brief discussion of the pitfalls of dividing antitrust enforcement authority across two agencies, saying it was a recipe for conflict.

"The problem is not that these things happen. The problem is that they can happen. And the fact that they do sometimes happen with other agencies, between other agencies other than your two, doesn't make it any more acceptable here. That is and ought to be a concern especially in something like antitrust," Lee said.

"Where you have even the possibility of multiple investigations involving the same conduct, the same actor or actors, the same substantive law," he added, "you have this almost unavoidable opportunity for conflict that really undermines either agency's ability to do what it needs to do,"