An Army general who helped broker the 1995 peace accord in Bosnia is President Clinton's choice for NATO commander and head of U.S. forces in Europe, White House Press Secretary Mike McCurry announced. Gen. Wesley K. Clark, 52, now heads the U.S. Southern Command in Panama. If confirmed by the Senate, Clark will succeed Gen. George Joulwan. The change of command is expected in July. The North Atlantic Treaty Organization post is a crucial one, given the alliance's plans to begin an eastward expansion in July and its attempts to forge a new relationship with Russia. Also, NATO is in charge of the current military mission in Bosnia-Herzegovina.