WASHINGTON — The House Benghazi Committee missed a self-imposed deadline to issue a report “before summer,” the latest setback for a probe that has gone on for more than two years and drawn scorn from Democrats who say its primary goal is to undermine Hillary Clinton’s presidential bid.

The panel’s chairman, Rep. Trey Gowdy, R-S.C., now says “the committee is working overtime to complete the investigation” and will “issue a report as soon as possible.” Clinton, who was secretary of state at the time of the deadly 2012 attacks, is expected to be nominated for president at the Democratic National Convention in Philadelphia in five weeks.

A congressional report on the Sept. 11, 2012 attacks in Libya that killed four Americans, including U.S. ambassador Chris Stevens, is certain to have ramifications for Clinton’s White House bid.

Gowdy, who has been dogged by charges of partisanship since the inquiry began in May 2014, disputed Democrats’ contention that the Republican-led investigation is focused on Clinton, saying in a statement that the panel’s work encompasses a host of federal agencies, including the Defense and State departments, the CIA, the White House and the intelligence community.

The committee has interviewed 107 witnesses so far, including 81 who had never before been questioned by Congress, Gowdy said. Nine of the new witnesses interviewed were eyewitnesses to the September 2012 attacks.

Gowdy has complained for months about the Obama administration’s reluctance to cooperate with the investigation, but he said in a statement Friday that he is grateful to all the witnesses who have taken the time to answer the panel’s questions.

“The testimony they provided helped complete our understanding of what happened in response to the Benghazi terrorist attacks,” he said.

Rep. Elijah Cummings of Maryland, the senior Democrat on the Benghazi panel, said the latest blown deadline for the Republican report “is no accident.”

Gowdy and other Republicans “are delaying their report until right before the presidential conventions for maximum political impact,” Cummings said in a statement.

“The American people see right through this partisan ploy,” Cummings added. “Republicans try to blame everyone else for their own delays, but that’s ludicrous. They waited more than a year to even request many of these interviews. Republicans have forfeited their credibility by delaying this report over and over again in order to push it into a presidential election year.”

Gowdy said in March that the committee had made progress after interviewing several top Obama administration officials, including national security adviser Susan Rice; her deputy, Ben Rhodes; and former Defense Secretary Leon Panetta.

In a March 9 email to The Associated Press, Gowdy promised a report “as soon as possible, before summer.”

Gowdy and other Republicans blame the Obama administration for impeding the investigation by repeatedly failing to produce needed documents or make witnesses available for interviews.

Most recently, Gowdy issued a subpoena to an assistant secretary of defense who claimed in a letter to the committee that officials could not find one of the requested witnesses.