The Trump Administration sought to block former acting attorney-general Sally Yates from testifying in the House investigation of possible links between Russian officials and Donald Trump's campaign, according to letters provided to the Washington Post.
The effort to keep Yates from testifying has further angered Democrats, who have accused Republicans of trying to damage the inquiry.
According to the letters, the Justice Department notified Yates this month that the Administration considers her possible testimony - including on the firing of former national security adviser Michael Flynn for his contacts with the Russian ambassador - to be off-limits in a congressional hearing because the topics are covered by attorney-client privilege or the presidential communication privilege.
The issue of Yates' testimony adds to the political controversy surrounding the House Intelligence Committee's investigation of Russian meddling in last year's election and any possible coordination between Trump associates and Moscow.
David O'Neil, a lawyer for Yates, met at the Justice Department to discuss the issue with government officials last Friday.