CARLSBAD, Calif. —  Republican presidential candidate John McCain on Tuesday urged Congress to adopt a sweeping overhaul of the nation's immigration laws and challenged critics to offer a better alternative.

The Arizona senator criticized his leading rivals, former Massachusetts Gov. Mitt Romney and former New York Mayor Rudy Giuliani, when a reporter asked about their opposition to a Senate compromise brokered earlier this month.

"Anyone who says we shouldn't pass this legislation, I would ask for their proposal," McCain said. "I have not heard their recommendation."

McCain said the U.S. cannot afford to continue allowing an estimated 12 million people to live in the country illegally. The Senate plan would establish a path to citizenship.

McCain repeated his plea for immigration reform minutes later before hundreds of technology executives at a conference sponsored by The Wall Street Journal. He also defended President Bush's decision to invade Iraq, while harshly criticizing how the war was handled under former Defense Secretary Donald Rumsfeld.

(Story continues below)

McCain praised current military leaders.

"Now we've got a new general, we've got a new strategy," he said. "It is working."