Former special counsel Robert Mueller will testify before two U.S. House of Representatives committees on July 24, one week later than originally scheduled, the chairmen of the panels said in a statement on Friday.

Mueller, who investigated Russian interference in the 2016 U.S. presidential election, has agreed to appear for "an extended period of time," House Judiciary Committee Chairman Jerrold Nadler and House Intelligence Committee Chairman Adam Schiff said. Mueller had been scheduled to appear for two-hour public hearings before each panel.

The earlier uncertainty presented a distraction for Democrats, who have billed Mueller's testimony as a potential watershed moment that could focus attention on segments of his 448-page report that raise troubling questions about President Donald Trump's efforts to impede the federal investigation.

The Judiciary Committee also sought to interview former Mueller aides Aaron Zebley and James Quarles behind closed doors. But Rep. Steve Cohen told reporters they would not appear after the Justice Department directed them not to.

Judiciary Committee members balked at the unofficial, earlier arrangement for Mueller, because many of the panel's less senior lawmakers would not get time to ask questions.

"Everyone on the committee wants an opportunity to examine Mr. Mueller," said Rep. David Cicilline, a senior House Judiciary Democrat. "We have been arguing for as much time as we can get. Obviously, we want to make sure that there's a full hearing."

Mueller's investigation was not able to establish evidence of collusion between Russia and the Trump 2016 presidential campaign. It made no final recommendation on whether there was obstruction of justice by Trump.