The Canadian government has written to the organisation to challenge the move.
"There is no evidence of casual transmission of the disease in Toronto," government health officer Dr Paul Gully said. "We challenge the WHO's assertion that Toronto is an unsafe place to visit."
Canadian officials say all the cases in the country can be linked to a single cluster of health workers.
Canada has had the highest incidence of SARS deaths outside of the Far East.
The country has 330 cases and 16 deaths, most of them in Toronto, which has a large ethnic Chinese population but the WHO recommendation not to visit brought an angry response.
"Where did this group come from? Who did they see? Who did they talk to?" said mayor Mel Lastman, referring to the WHO.
"Let me be clear. If it's safe to live in Toronto, it's safe to come to Toronto. I dare them to be here tomorrow," he told a news conference.
The WHO is helping to organise an international meeting on SARS in the Canadian capital Ottawa next week.
Major League Baseball officials advised caution when players visit Toronto. Officials initially told them to avoid signing autographs, but later amended that.
"While it is a concern, the risk of actual infection is still incredibly small," said Rob Manfred, executive vice president of labour relations for the baseball commissioner's office.
"The advice we're giving to the teams is basic health advice: wash your hands, avoid sharing food."