Democratic presidential candidate and former secretary of state Hillary Rodham Clinton delivers remarks at the Hillary Rodham Clinton Awards for Advancing Women in Peace and Security at Georgetown University on April 22, 2015 in Washington. (Photo by Win McNamee/Getty Images)

Democratic presidential candidate Hillary Rodham Clinton's campaign on Wednesday accused congressional Republicans of politicizing the deaths of four Americans in Benghazi, Libya, by dragging out an investigation until the waning months of the 2016 election.

The House Select Committee on Benghazi said its investigation would not be completed this year, as earlier planned. In a statement first reported by Bloomberg, the committee cited factors "beyond the committee's control," including what a spokesman characterized as delays and foot-dragging  by the Obama administration, for being unable to complete its work until sometime in 2016. That would mean that the committee's findings could be released during the primary season in the winter and spring of 2016, or after the general election contest begins over the summer.

Through a lawyer and her campaign chairman, Clinton challenged the committee chairman, Rep. Trey Gowdy (R-S.C.), to quickly call Clinton as a witness for a public hearing that would examine both the 2012 Benghazi attacks and Clinton's use of a private e-mail system while serving as secretary of state.

"The Gowdy commission's admission today that it will not finish its investigation until 2016 is the most telling evidence yet that their investigation is solely about playing politics in the 2016 presidential campaign," Clinton campaign chairman John Podesta said in a statement late Wednesday.

"Sadly, Republicans are determined to continue to exploit this tragedy in an effort to try and hurt her campaign," Podesta said.

Also Wednesday, Clinton lawyer David E. Kendall wrote to Gowdy to complain that the committee has delayed a response to a trove of Benghazi-related e-mails Clinton turned over in February. Kendall also said Clinton is willing to testify in a public hearing about the events surrounding Benghazi, and also about the e-mail system. The unorthodox e-mail system, in effect throughout Clinton's four-year term as secretary of state from 2009-2013, came to light only weeks ago.

The system meant that Clinton's e-mails were not preserved in the usual manner for government officials, if at all. She has said she turned over about 30,000 e-mails to the State Department last year, and had destroyed about the same number she deemed personal. The revelations gave new energy to the meandering congressional inquiries into the Benghazi deaths that blotted Clinton's State Department tenure.

Several investigations have found no scandal or coverup in the Benghazi attacks, but faulted the State Department for bureaucratic failures. Clinton has said she takes overall responsibility, since she was in charge of the department, but knew nothing about the security or other arrangements for the facility where U.S. Ambassador J. Christopher Stevens died. Three other Americans died there or at a related CIA facility nearby.

Clinton has volunteered to testify in a public hearing, and there is no need for a closed-door session as suggested by the committee,  Kendall said. Democrats have charged that the Republican-led committee wants to question Clinton in private so that they can control what is released or leaked from the session.

"Secretary Clinton's decision to seek the presidency of the United States does not and will not impact the work of the committee," Gowdy said in a statement released by the committee.