U.S. President Joe Biden and top congressional Republican Kevin McCarthy have reached a tentative deal to raise the federal government's $31.4 trillion debt ceiling, ending a months-long stalemate. However, the deal was described in terms that indicated it may not be absolute, and without any celebration -- an indication of the bitter tenor of the negotiations, and the difficult path it has to pass through Congress before the United States runs out of money to pay its debts in early June.