WASHINGTON — House Democrats on Monday moved to pre-empt the findings of a two-year Republican-led investigation into the attacks in Benghazi, Libya, in which four Americans were killed, by issuing their own 339-page report that cast the inquiry as a politically motivated crusade that wasted time and money.

The release of the Democrats’ report came amid signs that the House Select Committee on Benghazi, led by its chairman, Representative Trey Gowdy, Republican of South Carolina, was nearing the release of its official findings.

In the face of intense criticism, Mr. Gowdy has repeatedly defended the committee’s work as the most comprehensive examination of the attacks in Benghazi, which occurred on Sept. 11, 2012, and resulted in the deaths of Ambassador J. Christopher Stevens; a State Department official, Sean Smith; and two Central Intelligence Agency contractors, Tyrone S. Woods and Glen Doherty.

In recent days, the committee has reiterated longstanding complaints about lack of cooperation with the investigation by the Obama administration, including a statement by Mr. Gowdy on Monday citing obstruction by the State Department. The committee has also cited the refusal by the White House to have President Obama respond to written questions.