Maine’s U.S. Sen. Susan Collins is joining an effort to extend the federal Perkins Loan program for two years.

Collins says the popular program is to set expire on Sept. 30 and approximately 1,500 colleges and universities won’t be able to make the loans unless Congress acts. She says that would leave about a half million students without access to a key source of aid.

Collins, a Republican, is introducing the legislation along with Wisconsin Democratic Sen. Tammy Baldwin, Ohio Republican Sen. Rob Portman and Pennsylvania Democratic Sen. Robert Casey.

Collins says more than 4,000 Maine students received a Perkins Loan last year. She says the loans are important because they help fill gaps between the family’s ability to pay and other aid sources.