World stock index up but still below 5-1/2-month high

NEW YORK (Reuters) - A major global stock index rose slightly on Wednesday after three straight days of strong gains as investors braced for news on the United States' trade relations with Canada and China.Talks to renew the North American Free Trade Agreement (NAFTA) hinge on Canada after Monday's deal between the other parties to that pact, the United States and Mexico.Investors are also nervous ahead of a deadline for the next round of China-U.S. tariffs next week. MSCI's world equity index,..