A Republican senator threatened to walk out on the special deficit-reduction supercommittee if other members push for new cuts in defense spending.

The remark by Sen. Jon Kyl (R.,Ariz.), a defense finance expert and frequent budget negotiator, threatened to shatter any hope for compromise or bipartisan cooperation as the deficit panel held its first public meeting Thursday.

"I'm off of the committee, if we're going to talk about further defense spending," Sen. Kyl said at a luncheon organized by the conservative Foreign Policy Initiative, the American Enterprise Institute and the Heritage Foundation, referring to a conversation he had with panel ...