Sen. John McCain (R-AZ) on Thursday threatened to block the Trump administration’s nominees to key defense and national security positions over what he calls an insufficient response to the ambush in Niger earlier this month that resulted in the deaths of four U.S. soldiers. “I’d like to hear them say that they’re going to tell the Congress and the American people exactly what happened and why and why we weren’t told about it before,” McCain, who chairs the Senate Armed Services Committee, told reporters at the Capitol. “Nominees are not going through the United States Senate until we get the kind of cooperation we need.” The Arizona senator added that he has voiced his displeasure to Defense Secretary James Mattis directly. “We’re not moving [nominations] until we get the lines of communication and the information that we have to have constitutionally,” McCain told The Daily Beast. When asked if he is considering issuing subpoenas to compel the administration to respond, McCain said he considering calling a full committee meeting to discuss possible next steps. Earlier this week Sen. Jack Reed (D-R.I.), the ranking member on the committee, also accused the Pentagon of not being forthcoming enough.