US Treasury Secretary Jacob Lew Thursday urged Congress to raise the government's borrowing limit to avoid unnecessary self-inflicted crisis.

In a speech to the Commonwealth Club of California, Lew emphasized the need for Congress to act as soon as possible to avoid jeopardizing the full faith and credit of the United States and to avoid the economically harmful consequences of a US default or the threat of default.

"It is important to note that the debt limit has nothing to do with new spending. It has to do with spending that Congress has already approved and bills that have already been incurred. Failing to raise the debt limit would not make these bills go away. It would, though, have disastrous effects for our nation," Lew said in prepared remarks.

"We cannot afford for Congress to wait until some unknowable last minute to resolve this matter on the eve of a deadline. We cannot afford another unnecessary self-inflicted wound," he added.

When Congress returns from its recess in early September, lawmakers and the Obama administration will make tough fiscal decisions that include funding the government by Sept. 30 to avoid a federal shutdown and raising the debt limit.

Since the nation hit the debt ceiling of about 16.7 trillion U. S. dollars in May, the Treasury has been using extraordinary measures to finance government operations, which, it said, will probably only last until after Congress returns.

The receipt of tax revenues and the outflow of expenditures, Lew warned, are inherently unpredictable and so it is impossible for the Treasury to estimate when it will run out of options.

The country can't afford a repeat of the fiscal fight two years ago when a protracted debate about raising the debt ceiling brought the country to the brink of default, he said.