The White House and Congressional leaders remain adamant that the United States will not default on its $14.3 trillion national debt, less than three weeks before a deadline for raising the federal borrowing limit. But a bipartisan deal to put the nation on a sustainable fiscal path shows no sign of materializing. Weeks of negotiations have failed to yield a so-called ‘grand bargain’ to trim U.S. budget deficits by $4 trillion over 10 years. The impasse has prompted several fallback plans to raise the debt ceiling if the $4 trillion target is not met. Senate leaders are negotiating a plan that would allow President Obama to extend the federal borrowing limit even if majority votes in Congress do not materialize authorizing such a move. In the Republican-controlled House of Representatives, a vote is expected later this week that would tie a debt ceiling increase to a more-modest deficit reduction target, as well as a Constitutional amendment requiring a balanced budget.