As a result of stimulus spending and increased funding through the 2010 health-care law, the number of clinicians participating in a federal program to expand access to care in under-served communities has nearly tripled in the past three years.

About 10,000 doctors, nurses and other providers now participate in the National Health Serv­ice Corps, the highest number since the program was established in 1972, according to figures released by the Obama administration Thursday.

Officials estimated that the corps is serving about 10.5 million patients.

Since the 2009 fiscal year, the program has awarded medical professionals nearly $900 million in scholarships, loan repayments and other financial incentives in exchange for a commitment to provide two or more years of service in both rural and urban sites where clinicians are scarce. The new health-care law provided $290 million of that funding.

Officials said the program is expected to have an effect beyond that period because more than 80 percent of corps members continue to serve in high-need areas after they have fulfilled their commitments.

The causes of the clinician shortage include the aging of boomers, the retirement of doctors and an expected influx of more than 30 million Americans who will gain insurance through the health-care law beginning in 2014.

The Association of American Medical Colleges has estimated that a shortage of 91,500 physicians across all specialties will occur by 2020.