WASHINGTON — With tempers flaring, President Barack Obama and congressional Republicans clashed in an extraordinary live-on-TV summit today over the right prescription for the nation's broken health care system, talking of agreement but holding to long-entrenched positions that leave them far apart.

"We have a very difficult gap to bridge here," said Rep. Eric Cantor, the No. 2 House Republican. "We just can't afford this. That's the ultimate problem."

With Cantor sitting in front of a giant stack of nearly 2,400 pages representing the Democrats' Senate-passed bill, Obama said cost is a legitimate question, but he took Cantor and other Republicans to task for using political shorthand and props "that prevent us from having a conversation."

And so it went, hour after hour at Blair House, just across Pennsylvania Avenue from the White House.

Obama and his Democratic allies argued that a sweeping health overhaul is imperative for the nation's economic vitality. With the marathon policy debate available from start to finish to a divided public, Obama cast the health care crisis as "one of the biggest drags on our economy."

Sen. Lamar Alexander of Tennessee said Congress and the administration should start over and take small steps, including medical malpractice reform, high-risk insurance pools, a way to allow Americans to shop out of state for lower-cost plans and an expansion of health savings accounts.

"We believe we have a better idea," Alexander said. "Our views represent the views of a great many American people."