Treasury Secretary Tim Geithner said Sunday that it'd be "catastrophic" if Congress fails to increase the debt limit, as Republican leaders are threatening to do if spending is not also tamed.

"We know that the risk would be catastrophic," Geithner said on ABC's "This Week," warning party leaders not to "play politics with this."

"If you take it too close to the edge, then people will start to wonder, really, what are we doing, what are we thinking," he said, predicting that Congress will increase the ceiling in time.

Watch Geithner's appearance, via ABC News.