By Britain Eakin and Tim Ryan

This story is developing…

WASHINGTON – Nearly two years in the making, Special Counsel Robert Mueller confidentially submitted his report Friday on Russian interference in the 2016 U.S. election.

It remains unclear as to when, or whether, Attorney General William Barr will make the report public.

White House Press Secretary Sarah Sanders said the White House has not yet seen or been briefed on the report.

“The next steps are up to Attorney General Barr, and we look forward to the process taking its course,” Sanders said on Twitter Friday.

In a letter to the chairs and ranking members of the House and Senate Judiciary Committee on Friday, Barr said he would be prepared to brief them on the report’s “principal conclusions as soon as this weekend.”

“Separately, I intend to consult with Deputy Attorney General Rosenstein and Special Counsel Mueller to determine what other information from the report can be released to Congress and the public consistent with the law, including the special counsel regulations and the department’s long-standing practices and policies,” Barr wrote. “I remain committed to as much transparency as possible and I will keep you informed as to the status of my review.”

Representative Jerry Nadler, the chair of the House Judiciary Committee, reiterated his preference that as much of the report as possible be made public.

“A.G. Barr has confirmed the completion of the special counsel investigation,” Nadler, a New York Democrat said on Twitter Friday. “We look forward to getting the full Mueller report and related materials. Transparency and the public interest demand nothing less. The need for public faith in the rule of law must be the priority.”

Senate Judiciary Committee Chairman Lindsey Graham, R-S.C., noted Barr’s letter also states that the attorneys general who oversaw the probe never found reason to say Mueller took improper actions during the investigation.

Robert S. Mueller III

“I have always believed it was important that Mr. Mueller be allowed to do his job without interference and that has been accomplished,” Graham said in a statement Friday.

In a joint statement Friday afternoon, Speaker of the House Nancy Pelosi, D-Calif., and Senate Minority Leader Chuck Schumer, D-N.Y., called for “transparency” in handling the report.

“Now that Special Counsel Mueller has submitted his report to the attorney general, it is imperative for Mr. Barr to make the full report public and provide its underlying documentation and findings to Congress,” the leaders said in a statement. “Attorney General Barr must not give President Trump, his lawyers or his staff any ‘sneak preview’ of Special Counsel Mueller’s findings or evidence and the White House must not be allowed to interfere in decisions about what parts of those findings or evidence are made public.”

Senate Majority Leader Mitch McConnell, R-Ky., said he hopes the report will help give lawmakers guidance on how to protect against attempts to influence future elections.

“I am grateful we have an experienced and capable attorney general in place to review the special counsel’s report,” McConnell said in a statement. “Attorney General Barr now needs the time to do that.”

To date, Mueller has indicted or gotten guilty pleas from three Russian companies and 34 individuals. That includes six former Trump advisers and 26 Russian nationals, 12 of whom are intelligence officers Mueller charged with conspiring to hack Democratic Party emails that damaged Hillary Clinton.

From its inception 22 months ago, the special counsel’s investigation has been a continual thorn in the side of President Donald Trump.

Almost immediately, Trump took to Twitter and dubbed the investigation a “witch hunt,” which became a familiar refrain in his tweets condemning the investigation.

Trump had repeatedly denied that he or his campaign colluded with the Russian effort to sway the election in his favor, and insisted that Mueller’s report would vindicate him.

Despite several news reports indicating that President Trump wanted the investigation shut down, he has said he would let Attorney General Barr determine whether to release any of Mueller’s findings to the public.

The special counsel regulations required Mueller to submit a report to Barr explaining his prosecutorial decisions, but the decision about what details to make public rests with Barr.

Barr said during his confirmation hearing that he would support making public as much of the report as possible, “consistent with the law,” and said then he would author his own report as well.

Ordinarily, such an investigation would fall under the purview of the attorney general, but Barr’s predecessor, Jeff Sessions, recused himself from the matter in 2017, leaving Deputy Attorney General Rod Rosenstein in charge of the day-to-day aspects of the investigation.

Congress first learned that the FBI had been investigating Russian interference in the election, including a look at whether individuals in the Trump campaign had coordinated with that effort, from former FBI Director James Comey on March 20, 2017.

Trump fired Comey less than two months later, on May 9. Though the president cited Comey’s handling of the FBI’s investigation of Hillary Clinton’s use of a private email server during her tenure as secretary of state, he told NBC News’ Lester Holt two days later he had the “Russia thing” on his mind when he fired him.

In subsequent testimony before Congress, Comey said the president had asked him to let go of the FBI’s investigation of his short-lived national security adviser, Michael Flynn.

Flynn is one of several members of Trump’s inner circle swept up in the special counsel’s probe. He pleaded guilty to lying to the FBI about his contacts with former Russian Ambassador Sergey Kislyak, and his since cooperated with the investigation.

Mueller also indicted Trump’s former campaign chair, Paul Manafort, for crimes related to his prior lobbying work for pro-Russian politicians in Ukraine, and secured a conviction on eight counts of bank and tax fraud crimes from a Virginia jury.

Though Manafort pleaded guilty to separate but related charges in Washington, D.C., a federal judge recently determined that he breached his cooperation deal with Mueller by lying about his contacts with his long-time Russian associate Konstantin Kilimnik, whom the FBI believes has ties to Russian intelligence.

Longtime Trump adviser and GOP operative Roger Stone was the latest person in the president’s orbit to get swept up in Mueller’s investigation and is facing seven counts for lying to Congress, witness tampering and obstruction concerning his attempts to contact WikiLeaks during the 2016 election.

Rosenstein’s order appointing Mueller authorized the special counsel to investigate any other matters arising from the investigation, and allowed him to prosecute federal crimes arising from the probe.

Mueller survived several court challenges to his authority.