Jan 3 (Reuters) - Three-times Grand Slam ‌champion Stan Wawrinka began his farewell season with a battling victory ‌over Frenchman Arthur Rinderknech at the United Cup on Saturday and ‌declared that turning 40 had not dulled his competitive edge.

Switzerland's Wawrinka, who made his debut in 2002 and will celebrate his 41st birthday in March, said last month he wanted to bring ‍the curtain down on his career at the end ‍of the season.