(Adds Mueller aides testimony, fresh quotes, details and background)
By David Morgan and Richard Cowan
WASHINGTON, July 12 (Reuters) - Two U.S. House committees are considering a one-week delay for former Special Counsel Robert Mueller's planned July 17 testimony to allow more time for lawmakers to question him, sources told Reuters on Friday.
Mueller, who oversaw the federal investigation into alleged Russian interference in the 2016 U.S. presidential election, may now testify July 24, sources familiar with the plan said on the condition of anonymity because talks are continuing.
Lawmakers made conflicting statements about the hearing. Some said it would be delayed but others cautioned that a final agreement was not yet in hand.
In response to a query from Reuters, an aide to the House Judiciary Committee said in an email: "At this moment we still plan to have our hearing on the 17th and we will let you know if that changes."
The 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 committees have not officially announced any format. But Mueller had been expected to appear on Wednesday in separate two-hour public hearings before the House Judiciary and Intelligence committees.
The Judiciary Committee also sought to interview former Mueller aides Aaron Zebley and James Quarles behind closed doors. But Representative Steve Cohen told reporters they will not appear after the Justice Department directed them not to.
Judiciary Committee members have balked at the unofficial 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 Representative 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."
Under the new plan being considered, sources said the House Judiciary panel would get an additional hour for questions. But there was no sign of agreement among the committee's 24 Democrats and 17 Republicans, some of whom still could be left out.
"That's a decision that will be collectively be made, led by Chairman Jerry Nadler," said Representative Hakeem Jeffries, a Democrat who suggested there could be a way for some lawmakers to participate without asking questions of Mueller.
"Every single member of the House Judiciary Committee, on the Democratic and the Republican side, should be able to participate in the hearing in some way, shape or form."
Republican protests about the arrangements boiled over earlier this week, when Republican lawmakers accused House Intelligence Chairman Adam Schiff of upstaging the Judiciary Committee, despite its primary jurisdiction over special counsel investigations.
House Intelligence has 22 members, about equal to the number of Judiciary members who were initially expected to question Mueller.
In April Mueller submitted the findings of his nearly two-year investigation to the Department of Justice.
Mueller's investigation did not find evidence of collusion between Russia and the Trump 2016 presidential campaign. It made no final recommendation on whether there was obstruction of justice by President Donald Trump. (Reporting by David Morgan and Richard Cowan Editing by Jonathan Oatis and Bill Trott)
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