"We will reject GM wheat," said Keisuke Amagasa of the No! GMO Campaign. "If GM wheat is approved and commercial planting begins here, we will take action to prevent the import of wheat from Canada."

Japanese consumers are worried that biotech crops have not had enough testing to prove they are safe, Amagasa said.

Japan is one of Canada's biggest wheat markets, buying an average of 1.3 million tonnes a year.

Genetically modified wheat is not yet grown commercially, but Canadian and U.S. regulators for more than a year have been reviewing safety data for a variety developed by Monsanto Co. (MON.N: Quote, Profile, Research)

The wheat has been altered so it can withstand Roundup, a Monsanto herbicide. Regulators have not said how long their review will take.

The Canadian Wheat Board, which has a monopoly on most of Canada's wheat crop, has said government approvals would put most of its markets in jeopardy.

But Monsanto has promised it will wait to commercialize its wheat until it can keep it segregated from traditional grain and find customers who will buy it.

It has also promised it will not commercialize the wheat until regulators in the United States and Japan have also approved it.

"We recognize that there will be buyers who show a preference for non-biotech wheat," said Trish Jordan, a spokeswoman for Monsanto Canada.

"So what we're trying to do ... is to set up a system that maintains choice for all buyers," she said. The company has made its final submissions of regulatory data in Canada and the United States. It has also submitted preliminary safety data to Japan and several other countries, Jordan said.

"Even though we're a long way away from commercial introduction, there should be no reason why Japan cannot continue to buy Canadian wheat," Jordan said.

The Japanese delegates said millers had told them it would be too difficult and expensive to segregate GM wheat from traditional wheat.

"Millers have therefore said that unless Japanese consumers ... accept (genetically modified) wheat, they will not be able to sell it," said Koga Masaka of Consumers Union of Japan.