Sen. Rob Portman of Ohio joined 39 other Republicans in blocking a final floor vote on the nomination of Chuck Hagel to be secretary of defense, the first time in history the Senate has used a filibuster to delay the nomination of a candidate to head the Pentagon.

Although Portman said he eventually might join a majority of senators to end the filibuster, he said the nomination needs to be delayed until President Barack Obama provides Congress with more information on the attack on the U.S. consulate last fall in which four Americans died.

In addition, Portman and other Republicans are asking Hagel to provide copies of two speeches he gave on the Middle East.

In a statement, Portman said “at this point I’m inclined to oppose his nomination. But I find it hard to make a final determination until we have received responses to some reasonable requests for information that have been submitted by my colleagues. ‘’

“As a result, I do not support moving forward on a vote until some of these questions are answered,’’ Portman said. “If the White House would work with us to answer some of these reasonable questions, I would be supportive of moving forward with the debate and a vote.”