Fitch Ratings placed the U.S.'s pristine triple-A rating on watch for downgrade Tuesday as the federal government runs short on time to raise the nation's borrowing limit. The Fitch warning comes as the House and Senate work on competing plans to raise the U.S.'s borrowing limit and fully reopen the federal government. The Treasury Department, which has used extraordinary steps to continue paying its bills for roughly two weeks, says it will exhaust those powers on Thursday...Fitch said a failure by the government to honor interest or principal payments on U.S. Treasury securities would lead it to downgrade the U.S.'s sovereign issuer-default rating to "restricted default." It would also slash the affected issues to B-plus from triple-A. [WSJ]