June 4 (Reuters) - Canada's main stock index opened

lower on Tuesday, dragged by losses in energy and materials

shares as oil and copper prices fell, while investors await the

Bank of Canada's interest rate decision on June 5.

At 9:30 a.m. ET (13:30 GMT), the Toronto Stock Exchange's

S&P/TSX composite index was down 121.64 points, or

0.55%, at 21,995.05.

(Reporting by Shubham Batra in Bengaluru)