The White House has invoked the legal principle of executive privilege to block the release of the unredacted report by special counsel Robert Mueller on the Russia probe, escalating the battle between United States President Donald Trump and House Democrats.

Key points: The US Attorney-General says the Mueller report contains classified information

If Mr Barr is found in contempt, the case could possibly take months or years to resolve

House Democrats refuse to read the redacted version and are demanding the full report

The decision was announced just as the House Judiciary Committee recommended that Attorney-General William Barr be held in contempt of Congress over failure to release the full report.

The contempt resolution against Mr Barr now moves to the full House.

If it is approved, it would trigger a criminal referral to the US attorney for the District of Columbia, which would decide whether to prosecute.

"This was a very grave and momentous step that we were forced to take today to move a contempt citation against the Attorney-General of the United States. We did not relish doing this. But we had no choice," Judiciary Committee chairman Jerrold Nadler said.

The redacted Mueller report, released on April 18 by Mr Barr, left some questions about the probe unanswered.

Democrats have subpoenaed the unredacted report and the evidence Mr Mueller relied on, but Mr Barr, a Trump appointee, has refused to comply with the subpoena.

Mr Nadler declared the action by Mr Trump's Justice Department as a clear new sign of the President's "blanket defiance" of Congress' constitutional rights.

"Every day we learn of new efforts by this administration to stonewall Congress," Mr Nadler said.

"This is unprecedented."

White House press secretary Sarah Sanders said the action was rather a response to the "blatant abuse of power" by Mr Nadler, a Democratic representative.

"Neither the White House nor Attorney-General Barr will comply with Chairman Nadler's unlawful and reckless demands," she said.

In a letter to Mr Trump, Mr Barr explained that the special counsel's files contained millions of pages of classified and unclassified information.

He said it was the committee's "abrupt resort to a contempt vote" that "has not allowed sufficient time for you to consider fully whether to make a conclusive assertion of executive privilege".

A 'constitutional crisis'

Speaker of the House Nancy Pelosi said Democrats were surprised by Mr Trump's use of privilege. ( AP: J. Scott Applewhite )

Democrats on the committee said the Trump administration was trampling on Congress's duty to conduct oversight.



Mr Nadler said the Trump administration's refusal to provide the full Russia report to Congress presented a "constitutional crisis", leaving the panel no choice but to move forward with a contempt vote against Mr Barr.

Talks with the Justice Department broke down late Tuesday (local time) over the committee's subpoena for an unredacted version of the report.

House Speaker Nancy Pelosi suggested Democrats were surprised by the department's decision as last-minute talks failed.

Mr Barr released a redacted version of Mueller's report to the public last month, but Democrats subpoenaed the full document.

While the department rejected that demand, they allowed a handful of politicians to view a version of Mueller's report with fewer redactions. Democrats have said they will not view that version until they get broader access.

'Case closed' on Russia probe?

Special counsel Robert Mueller did not charge Mr Trump with obstruction of justice following the probe. ( AP: Andrew Harnik )

Executive privilege is the President's power to keep information from the courts, Congress and the public to protect the confidentiality of the Oval Office decision-making process.

If the committee holds Mr Barr in contempt, it would be the first step in what could be a protracted, multipronged court battle between Congress and the Trump administration.

However, the House would still need to send a criminal referral to the US attorney for the District of Columbia, a Justice Department official who is likely to defend the Attorney-General.

Democratic House leaders could also file a lawsuit against the Justice Department to obtain the Mueller report, though the case could take months or even years to resolve.

Some committee members have suggested they also could fine Mr Barr as he withholds the information.

US Attorney-General William Barr refused to attend the Mueller report hearing. ( AP: Andrew Harnik )

Mr Trump has defied requests from House Democrats since the release of the report last month, and Democrats are fighting the White House on several fronts as they attempt to learn more about the report by calling witnesses and obtaining Trump's personal and financial documents.

Republicans have largely united behind the President, with Senate majority leader Mitch McConnell declaring "case closed" on Mueller's Russia probe and potential obstruction by Mr Trump.

Mr Mueller said he could not establish a criminal conspiracy between the Trump campaign and Russia, but he did not reach a conclusion on whether Trump obstructed justice.

He also did not charge Mr Trump but wrote that he could not exonerate him either.

Ms Pelosi and Senate Democratic leader Chuck Schumer issued a joint statement calling it "a stunning act of political cynicism and a brazen violation of the oath we all take".

AP/Reuters