The PLO defied an eviction deadline Monday to vacate its U.N. observer mission under a U.S. anti-terrorist law as the General Assembly met in emergency session to consider ways to keep the mission open. A court battle appeared likely. The PLO observer, Labib Zehdi Terzi, made no move to shut the 13-year-old mission in a townhouse near Park Avenue and said he was awaiting U.S. legal action against the Palestine Liberation Organization. "Once we see what they do, then we will respond," he said in the U.N. Delegates Lounge. He said last week that U.S. authorities would have to drag him away. But no confrontation or physical move to shut the mission was expected.