Oil extended declines -- and has now lost more than a tenth of its value in three days -- as an increasingly aggressive U.S. trade policy fueled fears the world could be heading for a significant economic slowdown. Futures in New York fell as much as 2.6% after slumping 5.5% Friday. China struck a combative tone in a white paper released Sunday, blaming the U.S. for the collapse in trade talks and saying it won’t be pressured into concessions. That came after the White House rattled markets Friday by announcing tariffs on Mexican goods and terminating India’s designation as a developing nat...