CHICAGO (Reuters) Mar 03 - AARP, the lobbying powerhouse of 36 million U.S. senior citizens, will "ratchet up" pressure on the pharmaceutical industry to convince them not to block importation of cheaper prescriptions from Canada, the group's chief executive said on Wednesday.

"It's a fact of life -- people go to Canada, they go to Mexico" because they can't afford steep drug prices here, said William Novelli, chief executive officer at AARP, formerly the American Association of Retired Persons. "This is a national embarrassment that Americans have to go abroad to be able to afford their drugs."

A growing number of citizens are buying drugs from Canada, where they can cost up to 70 percent less than in the United States because of greater government regulation there.

Federal regulators say the practice is illegal and potentially unsafe, but individuals continue to do it, and some states and cities aim to aid their efforts.

Novelli said his group would write a letter within days to the Pharmaceutical Research and Manufacturers of America, the drugmaker's main lobby, spelling out actions it wants the industry to agree to.

"The pharmaceutical industry is not easy to convince, we all know that," he said. "I don't know if they'll ever come around on importation - but the least we can do is to get them to not choke off supply."

Pfizer Inc., the world's biggest drug company, last week said it cut off sales to two Canadian drug wholesalers, in a move analysts said was expected and related to the Canadian drug debate. Pfizer says it is trying to protect the pipeline of supply in Canada.

Other big drugmakers have also said they are keeping a close watch on where Canadian pharmacies ship their drugs.

AARP, for its part, took heat when it backed the Bush administration's legislation to overhaul the Medicare program for the elderly last year. Critics said it let drug makers off too easily by not giving the government the power to negotiate drug prices directly.

AARP, with 35.7 million members at the end of 2003, lost 60,000 members because of its backing of the law, Novelli said.