Aug 16 (Reuters) - Futures for Canada’s main stock index slipped on Monday as Prime Minister Justin Trudeau called an early election for Sept. 20. In calling for the snap election on Sunday, Trudeau said he needed a new mandate to ensure voters approved of his Liberal government’s plan to recover from the pandemic. September futures on the S&P/TSX index were down 0.3% at 5:20 a.m. ET. (Reporting by Sagarika Jaisinghani in Bengaluru; Editing by Shounak Dasgupta) Our Standards: The Thomson Reuters Trust Principles.