Washington ? Congress is under pressure to remedy a national doctor shortage that could worsen on July 1, when physicians who treat Medicare patients get a 10 percent pay cut.

Some say the situation is dire. One-third of the nation’s active doctors – or roughly 250,000 – are over 55 and likely to retire in the next decade. And while the number of applicants to U.S. medical schools is increasing, it hasn’t kept pace with the nation’s growing population, and graduating medical students are facing rising debt loads.

The issue is prompting bipartisan concern, particularly in rural regions.

A growing number of lawmakers want to stop the upcoming pay cut. And Congress is considering the Physician Shortage Elimination Act, which would spend millions to provide more scholarships for medical students and expand residency training programs throughout the country.

“While the president’s budget does not offer any ideas for addressing the physician-payment dilemma, it is undoubtedly one of the biggest challenges that Congress faces,” said Iowa Sen. Chuck Grassley, the top Republican on the Senate Finance Committee.

If Congress doesn’t act soon, doctors will receive a second pay cut – of 5 percent – on Jan. 1, 2009.

The shortage already has resulted in a rapid increase in the number of nurse practitioners, advanced nurses who can do the work of most primary-care physicians, and it has caused some doctors to delay their retirements.

“Part of the reason I’m not retiring is because I’m needed,” said Richard Guthrie, 72, an endocrinologist in Wichita, Kan. “Part of it is I’m having too much fun. As long as I’m in good health and there’s a need … I’ll keep doing it.”

Guthrie said there’s a dearth of physicians in his field and a dire need for his diabetes expertise, not only in Wichita, but also in rural Kansas, where he holds outreach clinics several times a month.

He said low reimbursement rates for Medicare are contributing to a critical shortage of physicians in fields such as family medicine and endocrinology because many graduating medical students, faced with high debt, want to go into higher-paying specialty fields such as cardiology or surgery.

If Congress worsens the problem by cutting reimbursements even more, Guthrie said he may be forced to cut his busy staff.

“It is a significant problem, which we all must address at the federal, state and local levels,” said Sen. Pat Roberts, R-Kan., who fears that if the doctor shortage worsens, the elderly will have the greatest difficulty getting medical care.