WASHINGTON — Canada might soon prohibit pharmacies from selling prescription drugs to mail-order customers, a move that would cut off a market that is increasingly popular with U.S. seniors eager to take advantage of Canadian price controls that make drugs there far cheaper than at home.

The proposal by the Canadian government could pre-empt a battle brewing in the United States over whether to crack down on consumers who buy their drugs through Canadian pharmacies.

According to spokesmen for both governments, President Bush discussed the issue privately with Canadian Prime Minister Paul Martin during a visit to Ottawa in November, sparking accusations from one trade group and a Democratic U.S. senator that Bush engineered the plan to stave off debate on an issue on which he holds an unpopular view.

White House spokesman Trent Duffy said late yesterday that Bush "made no such request of the Canadian government." With the debate expected to begin in Canada as early as next week, though, Bush's critics say they are poised to continue raising questions.

Bush has been reluctant to allow the purchase of drugs through Canada, saying that the practice could result in consumers buying unsafe, untested pharmaceuticals. The position was backed up last month by an administration task force that said legalized prescription-drug imports should be allowed only under strict federal supervision.

The practice is opposed by the politically influential pharmaceutical industry, a major financial backer of Bush. The industry gave almost twice as much to Republicans as to Democrats in the recent election cycle, according to the Center for Responsive Politics.

But the practice is supported by consumer advocates and many Democratic and Republican lawmakers who view Canadian pharmacies as a viable alternative for older Americans.

"When is the president going to stand up for the health of American patients and stop protecting drug-company profits?" Sen. Edward Kennedy, D-Mass., said in a statement released by his office yesterday.

It is technically illegal for Americans to import drugs from abroad, but they do anyhow in big quantities — about 10 million shipments a year, valued at $1.5 billion. Half of that business is from Canada.