Donald Trump set a lofty target for federal infrastructure spending Tuesday morning, saying that his administration would expend "at least double" the $275 billion over five years that Hillary Clinton has proposed.

"And you're really going to need more than that," Trump added in an interview with FOX Business. The GOP presidential nominee has consistently pledged to fix the nation's "crumbling roads and bridges" on the campaign trail, and has admitted it wouldn't come cheap. But his ambitious statement Tuesday is the first time he's ball-parked a cost estimate, and it drew an inquiry about how he planned to pay for it.

"We're going to go out with a fund," he said, specifying that it would be established with government bonds. "We'll make a phenomenal deal with the low interest rates, and we're going to have to rebuild our infrastructure. We have no choice."

That reasoning has been used by Clinton's own camp. When government is able to borrow at a low interest rate, "it is a crying shame if we are not making [those] kinds of investments," David Kamin, an economic advisor to the Democratic presidential nominee, said in May. "Because at those kinds of low interest rates, it means that it makes even more sense to try to make those kinds of long-term investments in infrastructure that can grow people's incomes."

The investments Clinton has in mind include $250 billion of direct spending, $25 billion for a national infrastructure bank, and a reauthorization of the Obama-era Build America Bonds program, which covered $181 billion of infrastructure spending during its lifespan from 2009 to 2010, according to the Treasury Department.

All of those numbers don't add up to the bare minimum of Trump's goal, of which the only supporting policy proposal he named Tuesday was a bond program. That leaves open the question of just how much taxpayers would be on the hook for his plan. A request to the campaign for additional details of the candidate's infrastructure agenda was unanswered as of publication.

Capitol Hill last addressed surface transportation issues in December, when it approved legislation authorizing more than $200 billion for the Federal-aid Highway Program between 2016 and 2020. The chairpersons and ranking members of the congressional transportation committees had not provided comment about potential spending proposals on top of that as of press time.