U.S. Sen. Bob Casey is calling for legislation to prevent an interest rate increase on federally subsidized student loans.

The current interest rate on Stafford loans is nearly 3.4 percent, and it's set to double July 1. Democrat and Republican bills to stop the rate increase failed to get enough votes to pass the Senate in early June.

Casey, a Pennsylvania Democrat, said in a speech in Philadelphia on Monday that Congress should draft a new bill that has bipartisan backing.

"It's the least Congress can do," he said.

The office of U.S. Sen. Pat Toomey, a Pennsylvania Republican, said the interest rate increase would amount to only few dollars a month and that the focus should be on the economy and on the rising cost of education in general.