A Canadian proposal to decriminalize possession of small amounts of marijuana is causing concern in the United States.

A committee of the House of Commons recommended Thursday that possession of 30 grams or less of marijuana no longer carry a criminal record.

Instead, people would face a civil penalty, such as a fine.

But U.S. Drug Control Policy Director John Walters warned that relaxed marijuana laws will wind up harming Canadians.

"When you weaken the societal sanctions against drug use," he said, "you get more drug use. Why? Because drugs are a dangerous addictive substance."

He said when U.S. attitudes about drug use were more lax in the 1980s, drug use soared.

"Don't repeat our pain," he said. "Learn from it if you can."

Possible trade retaliation

Robert Maginnis, a drug policy adviser to the Bush administration, warned that the U.S. would not look on any changes kindly.

"It creates some law enforcement problems and I think it creates some trade problems and some perception problems, especially in the U.S., with regard to whether Canada is engaged in fighting drug use rather than contributing to drug use," he said.

Maginnis said decriminalizing possession of small amounts of marijuana would encourage more illegal trade in the drug and he warned that the U.S. would likely retaliate.

"We're going to have to clamp down even stronger on our border if you liberalize and contribute to what we consider a drug tourism problem," he said.

"I don't want to get to the point where we're calling for a boycott of Canadian products."