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May 11 (Reuters) - Canada's main stock index closed in the green and hit its highest level in nearly three weeks on Monday, supported by gains in oil and metal stocks as investors weighed the impact of the Middle East conflict.

The Toronto Stock Exchange's S&P/TSX composite index .GSPTSE was up 0.18% at 34,138.88 and closed at its highest since April 21.

Materials .GSPTTMT and gold .SPTTGD both rose over 3% and energy stocks .SPTTEN gained 1.7% as precious metals and oil prices rose. GOL O/R

President Donald Trump's swift rejection of Iran's response to a U.S. peace proposal fueled concerns that the 10-week-old conflict will drag on and keep shipping through the Strait of Hormuz paralyzed, pushing up oil prices. O/R

"The headline is about stalemate in the Iran negotiations that is driving crude oil prices higher," Angelo Kourkafas, a senior global investment strategist at Edward Jones, said.

"For now, in the U.S. and globally, the AI story is driving the gains. In Canada, it's oil prices, the material sector, and that's probably going to persist," he said.

The Bank of Canada kept its key interest rate unchanged last month but Governor Tiff Macklem said if oil prices remained high and started to push up inflation, it might have to respond with consecutive rate hikes.

"It comes down to the fact that we are seeing accelerating earnings growth, and that is allowing investors to look through that headline volatility and focus on corporate fundamentals for the TSX," Kourkafas said.

Barrick Mining ABX.TO jumped 9% and was among the top gainers on the TSX index after the miner beat estimates for first-quarter profit, helped by record gold prices.

Cronos CRON.TO climbed 8% after the cannabis producer's first-quarter net revenue soared 40%, helped by sales in Israel and other countries that do not carry excise taxes.