WASHINGTON, US - The International Monetary Fund said Tuesday that a lending scheme to aid countries hit hard by the latest financial crisis has been increased to US$600 billion($833 billion).

The Washington-based Fund said that an additional 13 potential countries had agreed to join 26 nations in committing money to the so-called New Arrangements to Borrow (NAB), which was originally targeted at 500 billion dollars.

They also agreed to introduce more flexibility to the NAB, a standing set of credit arrangements under which participants commit supplementary resources for IMF lending when needed.

"Today's agreement on an enlarged NAB marks an important moment for multilateralism and the Fund, which will help the IMF's effectiveness in its response to crises and help strengthen the international financial architecture," IMF Managing Director Dominique Strauss-Kahn said.