WASHINGTON, D.C.: Although President Clinton will attempt to soften growing tensions between the U.S. and Mexico on immigration and the drug war on his trip to Mexico Monday, his chief mission will be to trumpet NAFTA's successes as he tries to extend the free trade agreement to all of Latin America by 2005. The President wants Congressional renewal of his "fast-track" authority, which gives Congress the power only to vote yes or no on trade pacts, with no chance to amend them. It will be a tough sell. Although the Administration can show positive numbers from the agreement -- NAFTA-generated trade among the U.S., Mexico and Canada reached a record $420 billion last year -- Congressional opponents led by Richard Gephardt counter by citing 118,000 U.S. jobs lost to cheaper Mexican labor. Most telling, opponents say, is that under NAFTA a $1.4 billion trade surplus in 1994 has plummeted to a $15.4 billion deficit. Congressmen are also unhappy that fast track has prevented them from adding labor and environmental safeguards to the pact, and vow not to let that happen on any hemisphere-wide agreement. As a result, the rest of the region is increasingly nervous about just how hard Clinton will fight for fast-track leverage. Clinton's seven-day Latin American swing is designed to allay those fears.