WASHINGTON, March 31 (Reuters) - More than half of U.S. doctors now favor switching to a national health care plan and fewer than a third oppose the idea, according to a survey published on Monday.

The survey suggests that opinions have changed substantially since the last survey in 2002 and as the country debates serious changes to the health care system.

Of more than 2,000 doctors surveyed, 59 percent said they support legislation to establish a national health insurance program, while 32 percent said they opposed it, researchers reported in the journal Annals of Internal Medicine.

The 2002 survey found that 49 percent of physicians supported national health insurance and 40 percent opposed it.

"Many claim to speak for physicians and represent their views. We asked doctors directly and found that, contrary to conventional wisdom, most doctors support national health insurance," said Dr. Aaron Carroll of the Indiana University School of Medicine, who led the study.

"As doctors, we find that our patients suffer because of increasing deductibles, co-payments, and restrictions on patient care," said Dr. Ronald Ackermann, who worked on the study with Carroll. "More and more, physicians are turning to national health insurance as a solution to this problem."

PATCHWORK

The United States has no single organized health care system. Instead it relies on a patchwork of insurance provided by the federal and state governments to the elderly, poor, disabled and to some children, along with private insurance and employer-sponsored plans.

Many other countries have national plans, including Britain, France and Canada, and several studies have shown the United States spends more per capita on health care, without achieving better results for patients.

An estimated 47 million people have no insurance coverage at all, meaning they must pay out of their pockets for health care or skip it.

Contenders in the election for president in November all have proposed various changes, but none of the major party candidates has called for a fully national health plan.

Insurance companies, retailers and other employers have joined forces with unions and other interest groups to propose their own plans.

"Across the board, more physicians feel that our fragmented and for-profit insurance system is obstructing good patient care, and a majority now support national insurance as the remedy," Ackermann said in a statement.

The Indiana survey found that 83 percent of psychiatrists, 69 percent of emergency medicine specialists, 65 percent of pediatricians, 64 percent of internists, 60 percent of family physicians and 55 percent of general surgeons favor a national health insurance plan.

The researchers said they believe the survey was representative of the 800,000 U.S. medical doctors. (Reporting by Maggie Fox; Editing by Will Dunham and Xavier Briand)