The survey of 11,950 primary care physicians by the Physicians' Foundation found 78 percent of primary care physicians say they believe there is an existing shortage of primary care doctors in the United States.

Forty-nine percent -- of the more than 150,000 practicing doctors -- say during the next three years they plan to reduce the number of patients they see or stop practicing entirely.

The reported reasons for the widespread frustration among doctors include: increased time spent dealing with non-clinical paperwork, difficulty receiving reimbursement from insurance companies and burdensome government regulations.

"Tens of thousands of primary care doctors face the same problems as millions of ordinary citizens: frustrations in dealing with HMOs and government red tape," Sandra Johnson, board member of the Physicians' Foundation, said in a statement.

"The thing we heard over and over again from the physicians was that they're unhappy they can't spend more time with their patients, which is why they went into primary care in the first place."

The survey, by Merritt, Hawkins & Associates, has a margin of error of 1 percentage point.