Two top Clinton aides, Cheryl Mills and Jake Sullivan, will appear before the House Select Committee on Benghazi next month, but when will the committee interview several other top Obama administration officials and Clinton allies?

House Benghazi Committee Chairman Trey Gowdy, R-S.C., described how the committee intends to finish its work before the calendar year 2015 ends, in an exclusive interview with the Washington Examiner. Gowdy discussed his desire to interview key Obama and Clinton operatives, including former State Department deputy chief of staff Huma Abedin, State Department undersecretary for management Patrick Kennedy, and State Department chief of staff Jon Finer. He also indicated his frustration at the lack of information former State Department policy planning director Jake Sullivan has produced.

Sullivan now serves as a top foreign policy adviser to Democratic presidential candidate Hillary Clinton, Abedin is a top aide and confidant of Clinton, and Kennedy and Finer remain at the State Department.

Gowdy said he wants all of the documents relating to these individuals before interviewing them, but continues to face an uphill battle.

"What can I do to make the Department of State produce Jake Sullivan's emails to me? I've asked. I've sent a subpoena. I don't know what else I can do. I can't send the FBI to get him," Gowdy said. "I have a freshman in college who could go pull up all of her emails and have them printed off by this afternoon. I don't know what takes so long, but it's been months and months and months. And we still don't have all the documents we've asked for."

Sullivan will appear before the committee during the first week of September, as the Examiner previously reported. The committee expects to interview Clinton on Oct. 22, and her right hand woman, Abedin, should come soon too.

"When is Huma? I know for a fact that Dana is negotiating that date with her attorney [right now] and with respect to Patrick Kennedy, he would be towards the end of the folks that we wanted to interview in a natural chronology," Gowdy said. "My goal is still to have this investigation completed before the end of 2015. So the best answer I can give you is before the end of 2015."

Dana is Lt. Gen. Dana K. Chipman, who Roll Call profiled as the senior military lawyer for the Army for four years as judge advocate general at the Pentagon.

Gowdy said Finer, Kerry's chief of staff, will appear "sooner rather than later," and Finer's intransigence has worn on Gowdy's patience.

"Very few things make me mad with impatience, but listening to House Democrats complain about the pace of the investigation while Jon Finer and others refuse to give me documents is one of those things," he said. "So they're going to have to pick their complaint. You can't complain about the pace of an investigation when your Democrat executive branch entities are the sole reason you're going at a slower pace than you want."

Gowdy emphasized that his committee's work has much to do beyond meeting with Clinton in October. He said the committee has interviewed 40 people, many of whom had never spoken with other committees investigating the facts surrounding Benghazi, and that "probably 50" interviews remain yet to be completed. The House formed the Benghazi Committee in May 2014, with the support of seven Democratic members and 225 Republican representatives.

UPDATE: Alec Gerlach, State Department spokesman, issued the following statement in response to Gowdy:

"Claims that we have been slow to respond to the increasing demands of the Benghazi Select Committee are neither true nor reflective of the effort being expended by an entire team of professionals at the State Department. Since April, the Department has produced more than 24,000 pages of documents to the Benghazi Committee, bringing to 66,000 pages the total produced to the committee since it was formed. The Department has also made 31 witnesses available to the committee for interviews, including five this month. We will continue to respond to the Benghazi Committee's requests, but as they mount and modify over time, so too must we plan accordingly for the time and resources they consume."