Panetta: Syria intervention risky, but possible (CBS/AP) WASHINGTON - The nation's top military leader said Wednesday that U.S. was considering "all possible additional steps" including "potential military options" in Syria, but stressed the administration was focused on "diplomatic and political approaches rather than a military intervention." "What doesn't make sense is to take unilateral action right now," Defense Secretary Leon Panetta told the Senate Armed Services Committee about advising President Barack Obama to dispatch U.S. forces. I've got to make very sure we know what the mission is ... achieving that mission at what price. Still, he would "not rule out any future course of action," amid continued pressure from several lawmakers for the U.S. to do more to end President Bashar Assad's deadly crackdown on his people The panel's top Republican, Sen. John McCain of Arizona, said the estimated 7,500 dead and the bloodshed calls for U.S. leadership that a Democratic president, Bill Clinton, displayed during the Bosnian war in the 1990s and that Mr. Obama eventually showed on Libya last year. In past situations, America has led. We're not leading, Mr. Secretary," McCain told Panetta. U.N. humanitarian chief heads for Homs Syria's Assad defies pressure to end fighting The Pentagon chief later added that the United States is not holding back and is leading in Iraq, Afghanistan, Syria and the war on terrorism. Testifying before the committee, Army Gen. Martin Dempsey and Panetta offered a cautionary note to the call by McCain to launch U.S. airstrikes against Assad's regime. "This terrible situation has no simple answers," Panetta told the panel. U.S. puts forth new U.N. resolution on Syria U.S. general: Syrian air defense may be problem Mr. Obama has resisted calls to step into the turmoil in Syria to stop Assad's crackdown on protesters. The Pentagon chief said the United States is currently focused on isolating the Assad regime diplomatically and politically, arguing that it has lost all legitimacy for killing its own people. Dempsey said among the military options are enforcement of a no-fly zone and humanitarian relief. He said a long-term, sustained air campaign would pose a challenge because Syria's air defenses are five times more sophisticated than Libya's. He said Syria's chemical and biological weapons stockpile is 100 times larger than Libya's. He said suppressing the Syrian air defenses would take an extended period of time and a significant number of aircraft, an effort that would have to be led by the United States. One complication, Panetta and Dempsey pointed out, is the location of the sophisticated air defenses: populous neighborhoods. If the U.S. unleashed its military power, that could mean scores of unintended deaths. "We also need to be alert to extremists, who may return to well-trod ratlines running through Damascus, and other hostile actors, including Iran, which has been exploiting the situation and expanding its support to the regime," Dempsey said. And we need to be especially alert to the fate of Syria's chemical and biological weapons. They need to stay exactly where they are. McCain, along with Sens. Lindsey Graham, R-S.C., and Joe Lieberman, I-Conn., have called for U.S. military involvement. But the issue has divided Republicans, with House Speaker John Boehner, R-Ohio, insisting on Tuesday that the situation is too muddled and U.S. military involvement would be premature. Committee Chairman Carl Levin, D-Mich., said there is no consensus on how to get Assad to leave.