Updated, 3:40 p.m.

As the White House ramps up its push to woo young voters by urging Congress to head off a scheduled increase in student loan interest rates, GOP presidential front-runner Mitt Romney struck back Monday, throwing his support behind an extension of the current rates at a campaign event outside Philadelphia.

The former Massachusetts governor made the announcement at a press availability with U.S. Sen. Marco Rubio, the first joint appearance of Romney and the Florida Republican whose name is often floated as a top choice for his running mate.

“There’s one thing that I wanted to mention, that I forgot to mention at the very beginning, and that was that particularly with the number of college graduates that can’t find work or that can only find work well beneath their skill level, I fully support the effort to extend the low interest rate on student loans,” Romney said at the end of a seven-minute joint news conference with Rubio.

“There was some concern that that would expire halfway through the year, and I support extending the temporary relief on interest rates for students as a result of student loans, obviously, in part because of the extraordinarily poor conditions in the job market.”

The announcement comes on the heels of an Associated Press report showing that half of recent college graduates are jobless or underemployed.

Obama devoted his weekly address to the topic of federal student loans, pushing for a renewal by Congress of the 2007 law keeping rates at 3.4 percent. The rates will revert to 6.8 percent in July if Congress does not act. According to the White House, more than 7 million students would be affected by the rate increase.

On Monday, the White House called Romney’s support of the extension inconsistent with past support for education cuts.

“Mitt Romney continues to make promises that he can’t keep,” said Lis Smith, a spokeswoman for the Obama campaign. “While he previously endorsed the Ryan budget, which would make deep cuts to Pell Grants and allow student loan rates to double, and last week said that he would gut the Department of Education to pay for his tax plan, today we heard yet another — and contradictory — position from Romney on student loans.”

Also on Monday, Sen. Tom Harkin (D-Iowa), chairman of the education committee, said he plans to introduce a bill later this week that would extend the lower interest rate for one year. He said lawmakers could then consider enacting a more permanent modification when the Higher Education Act comes up for renewal next year.

“Unfortunately, the clock’s ticking,” he said in a conference call with reporters. “We need Republicans in Congress to work with us.”

Harkin said he opposes using other cuts in education to pay for the extension, which is estimated to cost $6 billion, but he had not yet determined how to pay for it. Obama is slated to speak in Harkin’s home state on Wednesday about the rising cost of college education and mounting student debt.

The office of House Speaker John A. Boehner (R-Ohio) responded to Romney’s move by noting that members of both parties on both sides of the Capitol “will be working on this issue in the coming months.”

But the top House Republican also framed the expected rise in Stafford loan rates as the result of Democratic policies.

“The rising cost of tuition is a serious problem for students and their families, so it’s unfortunate that Washington Democrats put in place a law that would double student loan rates,” Boehner spokesman Michael Steel said.

Sen. Charles E. Schumer (N.Y.), the No. 3 Senate Democrat and the party’s messaging chief in the upper chamber, said that “what Mitt Romney said — following the president’s lead — is a good thing, but the proof is in the pudding.”

“It’s unclear if it’s simply a way to get on board a popular issue or an effort to actually get something done,” Schumer said. “We’ll see how it plays out over the next few weeks. If Mitt Romney says to the Senate and House Republican leadership, ‘Find a compromise pay-for,’ that would be very helpful.

“But if they’re just going to say we’re for it — but not for paying for it any way that can pass and not for not paying for it — then it’s a game,” he added.

Obama’s reelection campaign has been searching for ways to reignite young voters, who provided much of the enthusiasm that helped propel the president to victory four years ago. A poll last week by Georgetown University and the Public Religion Research Institute found that top issues for young voters are jobs and unemployment. Education was nearly tied with the federal deficit for second place.

“We’re not particularly concerned by the president’s appeal to young voters. We think that he has the right vision and the right answers that are gonna appeal to those voters,” Obama’s campaign policy director, James Kvaal, said Monday. “The topic that we’ve been discussing today is a great example of why.”

On Tuesday, Obama will travel to Colorado and North Carolina to continue his student-loan push with campaign events at the University of Colorado at Boulder and the University of North Carolina at Chapel Hill. On Wednesday, he will visit the University of Iowa.

Romney has often made the case along the trail that young people should support his campaign rather than Obama’s because of the country’s economic struggles.

Romney renewed that argument Monday, contending that young voters “are questioning the support they gave to President Obama three-and-a-half years ago.”

“I think young voters in this country have to vote for me if they’re really thinking of what’s in the best interest of the country and what’s in their personal best interest, because the president’s policies have led to extraordinary statistics,” Romney said.