US President Barack Obama summoned top lawmakers to a Saturday meeting to try to salvage a deal on the government's borrowing limit from the wreckage of deficit talks whose collapse pushed the world's largest economy closer to a catastrophic default. With the Treasury set to run out of money to pay all of its bills on August 2, Obama said the window may have closed for a "grand bargain" of spending cuts and tax increases in exchange for Congress raising the $14.3 trillion debt ceiling. Credit rating agencies also want spending restraints for the United States to keep its prized AAA rating that makes Treasuries the solid foundation for global investors and lowers borrowing costs for state governments, businesses, homeowners and consumers. "We have now run out of time," Obama said on Friday after John Boehner, the top Republican in Congress, broke off talks on a deficit reduction package worth more than $3 trillion over 10 years.