http://www.cbsnews.com/stories/2007/01/12/politics/main2355951.shtml

(CBS/AP) As President Bush tries to sell his new Iraq policy, his administration is keeping an eye on another threat — Iran, reports CBS News national security correspondent David Martin.

U.S. officials tell CBS News that American forces have begun an aggressive and mostly secret ground campaign against networks of Iranians that had been operating with virtual impunity inside Iraq.

The chairman of the Joint Chiefs of Staff told Congress on Friday that Iranians are now on the target list.

"Twice in the last two or three weeks, in pursuit of those networks, when we have gone and captured those cells, we've captured Iranians," said Gen. Peter Pace.

According to U.S. military figures, 198 American and British soldiers have been killed, and more than 600 wounded by advanced explosive devices manufactured in Iran and smuggled in through the southern marshes and along the Tigris River. Attempts to disrupt these networks, combined with the decision to send a second aircraft carrier to the Persian Gulf as a warning to Iran, significantly raises the stakes, according to former Assistant Secretary of State Martin Indyk.

"It's going to have, you would expect, some rather serious consequences," he said.

Defense Secretary Robert Gates tried to assure the Senate Armed Services Committee the U.S. military will not widen the war into Iran.

"We believe that we can interrupt these networks that are providing support through actions inside the territory of Iraq and there is no need to attack targets in Iran itself," he said.

But with the future of oil-rich Iraq at stake, the revolutionary leaders of Iran are not likely to back down.

"Since the president has taken the gloves off, I would expect that they would respond by taking the gloves off, too," Indyk says.

Pentagon sources tell CBS News the U.S. military has planned covert cross-border raids into Iran — but so far none has been approved.

Meanwhile, Sen. John McCain defended President Bush's Iraq plan on Friday as a difficult but necessary move, parting company with lawmakers fiercely resisting the military build up.

"I believe that together these moves will give the Iraqis and Americans the best chance of success," said McCain, R-Ariz., a leading presidential contender for 2008.

McCain also took a shot at Democrats who say the U.S. must bring home some troops within four to six months.

"I believe these individuals ... have a responsibility to tell us what they believe are the consequences of withdrawal in Iraq," he said. "If we walk away from Iraq, we'll be back, possibly in the context of a wider war in the world's most volatile region."

McCain spoke at the Senate Armed Services Committee, where Gates and Gen. Peter Pace, chairman of the Joint Chiefs of Staff, spent a second day on Capitol Hill defending the president's strategy.

As they did, Democrats continued considering strategies for challenging Mr. Bush's war policies. One influential lawmaker, Rep. John Murtha, D-Pa., said he'd like to require closing the U.S. prison at Guantanamo Bay, Cuba, and better training for troops heading to the war zone as conditions of Congress providing more money for Iraq.

"We have to close the prison at Guantanamo," said Murtha, who heads the House panel that controls the Pentagon's budget. He said Democrats would decide later whether to pursue the idea.

The Bush administration has said military the detention center is still needed. It holds almost 400 detainees suspected of links to al Qaeda and the Taliban.

Gates and Pace on Friday assured lawmakers there were no immediate plans to attack targets in Iran. In his speech this week on Iraq, Mr. Bush vowed to disrupt Iran's aid to insurgents in Iraq and "destroy the networks providing advanced weaponry and training to our enemies in Iraq."