As death toll climbs, pressure builds for Mideast cease-fire

More than 500 Palestinians and 27 Israelis have died in the conflict that began two weeks ago. Palestinians reported that Israeli tanks shelled a hospital, killing at least four. The Israelis say they are focused on destroying Hamas rockets and a network of tunnels used by militias. Chief foreign affairs correspondent Margaret Warner reports on the mounting U.S. and U.N. pressure for a cease-fire.