WASHINGTON — The chairman of the Joint Chiefs of Staff said today the next 12 to 18 months will be critical to reversing momentum gained by insurgents in Afghanistan, with nothing short of the war-torn nation's security at stake.

Not only that, Adm. Mike Mullen told the Senate Armed Services Committee: "Our future security is greatly imperiled if we do not win the wars we are in."

Further, he added, "The outcome of today's conflicts will shape the global security environment for decades to come."

Mullen and Defense Secretary Robert Gates appeared together on Capitol Hill to defend the Pentagon's request to spend $192 billion on the wars in Iraq and Afghanistan for the next year and a half. Of that amount, $33 billion would be spent to widen the U.S. commitment in Afghanistan by sending 30,000 more troops there by fall.

At one point, Gates noted that there will be another review of Afghan policy later this year. "If our strategy is not working," he said, "we will not just punch ahead blindly."

Many anti-war Democrats are skeptical of endorsing such a hefty sum, even though President Barack Obama says more troops would be necessary to ultimately end the campaign.