Defense chief huddles with GOP ahead of trade vote
Defense Secretary Ashton Carter huddled with Senate Republicans ahead of an initial vote on "fast track" trade legislation.
The Pentagon chief was invited to the weekly GOP lunch by Majority Leader Mitch McConnell (R-Ky.) and Sen. John Barrasso (R-Wyo.).
A GOP aide said Carter was expected to discuss a controversial trade bill, which the Senate will take a procedural vote on later Tuesday afternoon.
Carter "will speak about how the pending trade legislation will strengthen our national security," the aide said.
A defense official confirmed Carter's attendance and said he was expected to discuss trade legislation and answer national security questions. 
The bill would allow President Obama to get his trade deals approved by a simple majority vote in Congress.
The issue has split Senate Democrats, pitting those on the side of their leader, Harry Reid (Nev.), against those who side with the administration.
McConnell is also facing some resistance within his own party, with Sen. Jeff Sessions (R-Ala.) saying last week he's skeptical of the legislation.
And both sides are digging in ahead of the vote.
Sen. Orrin Hatch (R-Utah), who has been at the center of debate to try to reach a deal, said Tuesday he's "really basically shocked" the legislation could be blocked by a procedural vote.
"We had an agreement," he said.
Sen. Dick Durbin (D-Ill.) said it is "in doubt" whether the afternoon procedural vote will be successful.
— Updated at 1:48 p.m.