WASHINGTON, D.C.: Congressional negotiators are working furiously to prevent a possible third federal government shutdown and a first- ever federal default. With federal temporary spending authority set to run out at midnight on Friday, lawmakers are close to sending president Clinton two mammoth spending bills. The first would prevent a federal default by extending federal borrowing authority through September 1997, a move that would require raising the debt ceiling to $5.5 trillion. The second measure would spend roughly $160 billion to fund federal departments and agencies in the final six months of fiscal year 1996. With passage of the first measure likely, Congressional leaders and the administration have turned their attention to the funding bill. The administration is seeking an additional $8 billion for education, high technology and other programs on President Clinton's agenda. The President also wishes to delete provisions in the bill allowing increased logging on federal lands and easier development of wetlands in California's Mojave desert. Congress has met the President halfway, restoring nearly $4 billion to the spending bill. But the White House is still demanding an additional $1.8 billion for Head Start, veterans medical care and other programs. As part of an agreement with the White House, both bills will be packaged with three unrelated measures: a line-item veto, a Social Security measure that will permit Social Security recipients who continue working after age 65 to keep more of their benefits, and a Regulatory Reform bill that would allow small businesses to challenge government regulation in court. GOP leaders are hoping that these add-ons will induce the more conservative Republican lawmakers to accept raising the debt ceiling and permit deficit spending for another year and a half.