Asian stocks ended mixed on Wednesday ahead of the U.S. Federal Reserve's interest-rate decision under Chairman Kevin Warsh later in the day and Friday's signing of the U.S.-Iran interim peace agreement. The signing of the Memorandum of Understanding in Switzerland is likely to pave the way for a 60-day negotiating period to address key issues that have plagued U.S.-Iran diplomacy for decades, potentially unlocking Iranian oil exports and beginning a phased rollback of sanctions in exchange for nuclear curbs. The Fed is seen holding rates steady today despite concerns over persistent inflation, with all eyes on Kevin Warsh's first FOMC press conference. China's Shanghai Composite index edged up 0.40 percent to close at 4,108.08, while Hong Kong's Hang Seng index fell 0.74 percent to 24,312.16. Japan's Nikkei average surged 0.72 percent to 69,902.25, closing at a record high for a third straight session, and South Korea's Kospi index rallied 1.58 percent to 8,864.24.