Asian stocks slipped on Monday after Wall Street sank amid plunging crude oil prices, keeping investors on edge ahead of an expected U.S. rate rise by the Federal Reserve later in the week. MSCI’s broadest index of Asia-Pacific shares outside Japan was down 0.9 percent after touching a 2-1/2-month low. Japan’s Nikkei fell 2.3 percent on the yen’s appreciation, while South Korea’s Kospi retreated 1.3 percent.