US Secretary of Education Arne Duncan speaks about student loan interest rates April 20 during the Daily Press Briefing in the Brady Press Briefing Room at the White House. (SAUL LOEB/AFP/GETTY IMAGES)

The Obama administration on Friday urged Congress to step in to prevent a doubling of the interest rate on a massive federal student loan program this summer, affecting an estimated seven million borrowers.

Congress halved the interest rate on federally subsidized Stafford loans to 3.4 percent in 2007. If the legislation isn’t extended, the rate reverts to 6.8 percent in July.

In a news conference Friday, Education Secretary Arne Duncan said the higher rate would add $1,000 a year to the repayment cost of the average loan.

“Families and students are struggling to meet these costs, and there’s no reason we should add to their burden,” he said.

Five years ago, the measure passed with bipartisan support. This spring, the legislature is divided along party lines. Republican leaders accused the president of amplifying that division because it is an election year.

“Bad policy based on lofty campaign promises has put us in an untenable situation,” Rep. John Kline (R-Minn.), chairman of the House education committee, said in a prepared statement.

Student loan debt stands at $870 billion nationally, surpassing credit card and car-loan debt, according to a March report from the Federal Reserve Bank of New York. The average loan has doubled in size since the mid-1990s, and the share of students who borrow has risen from roughly one-half to two-thirds, mirroring a sharp rise in college tuition.

“With today’s tough economy and high unemployment rate among young Americans, we should not be asking middle-class students and families to shoulder even more student loan debt,” Sen. Tom Harkin (D-Iowa), chairman of the Senate education committee, said in a statement.

Congressional Democrats have introduced bills to extend the lower interest rate for another year at an estimated cost of $6 billion. But Democratic leaders have acknowledged that the measures might not pass.

Last month, student advocates presented congressional leaders with 130,000 letters protesting a higher rate. They would prefer something more than a one-year commitment.

But Rich Williams, of the U.S. Public Interest Research group, said, “We’d be happy if they’d take one step in the right direction.”