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Defense Secretary Chuck Hagel and chairman of the Joint Chiefs of Staff Gen. Martin Dempsey both warned Congress on Wednesday about the unintended consequences of a U.S. military intervention in Syria. Hagel also provided the first details of the Pentagon's efforts in assisting Jordan's military for the possibility of having to secure Syria's chemical weapons stockpile, including $70 million worth of training and equipment.

Appearing before the Senate Armed Services Committee both Hagel and Dempsey cautioned that a U.S. military intervention in Syria could have unintended consequences and should be reserved as a "last resort."

Two years of fighting to bring down the regime of Syrian President Basher al Assad have killed an estimated 70,000 Syrians and created a million refugees. Both Democratic and Republican senators on the committee have advocated the Obama administration consider some form of U.S. military assistance to assist the Syrian opposition in the form of a no-fly zone or the establishment of a humanitarian aid corridor.

"We have an obligation and responsibility to think through the consequences of direct U.S. military action in Syria," said Hagel. He added that "military intervention at this point could hinder humanitarian relief operations. It could embroil the United States in a significant, lengthy, and uncertain military commitment."

More importantly he warned that it could have "the unintended consequence of bringing the United States into a broader regional conflict or proxy war. " He stressed that "the best outcome for Syria - and the region - is a negotiated, political transition to a post-Assad Syria."

He later used blunter language in describing how all factors should be weighed in considering a U.S. military option in Syria. "You better be damn sure, as sure as you can be, before you get into something, because once you're into it, there isn't any backing out, whether it's a no-fly zone, safe zone, protect these - whatever it is. Once you're in, you can't unwind it. You can't just say, well, it's not going as well as I thought it would go, so we're going to get out.

Gen. Dempsey also told the committee that " before we take action, we have to be prepared for what comes next." He noted that the use of force in an area like Syria where the ethnic and religious divisions "dominate" is "unlikely to produce predictable outcomes." He explained that such a scenario "is not a reason to avoid intervention in conflict, rather, to emphasize that unintended consequences are the rule with military interventions of this sort."

In his opening remarks Hagel presented the most detailed outline yet of American efforts in helping Jordan prepare for the possibility of having to secure the Assad regime's large chemical weapons stockpile should the regime collapse. For much of the past year Pentagon officials have declined to provide details about such efforts, instead making vague references about contingency planning with regional partners for such a scenario.

Hagel told the committee that the Pentagon "has plans in place to respond to the full range of chemical weapons scenarios." He disclosed that the U.S. has provided $70 million in funding to Jordan "for training and equipment to detect and stop any chemical weapons transfers along its border with Syria, and developing Jordanian capacity to identify and secure chemical weapons assets."

However, when Sen. John McCain asked Gen. Dempsey if he was confident that American troops would be able to secure Syria's chemical weapons, Dempsey said, "Not as I sit here today, simply because they've been moving it and the number of sites is quite numerous."

According to Hagel, the U.S. military has also prepared for other contingencies such as " the potential spillover of violence across Syria's borders that could threaten Allies and partners." Furthermore, he said, the Pentagon had "been developing options and planning for a post-Assad Syria," though he said he was not able to provide details in public.

Hagel also announced that last week he ordered the deployment to Jordan of a headquarters element from the 1 st Armored Division based at Fort Bliss, Texas.

They will replace the several hundred American military members from various units who have been in Jordan since last summer working with the Jordanian military in contingency planning related to Syria's chemical weapons, humanitarian efforts and preventing a spillover of violence from Syria into Jordan.

A Defense official said the headquarters will provide "a cohesive command and control element with our Jordanian counterparts." The official also said that if needed its structure would enable it to "be capable of establishing a Joint Task Force headquarters that would provide command and control for Chemical Weapons response, humanitarian assistance efforts and stability operations."

Hagel also referred to the other forms of assistance the U.S. is providing to Syrian refugees and opposition groups. That includes $385 million in assistance to help ease the humanitarian and refugee crisis in Syria, as well as $117 million in non-lethal assistance to the Syrian opposition in the form of communications and medical equipment.

The Defense secretary told the committee that he would be visiting Jordan next week as part of a Middle East tour that will see him making stops in Israel, Egypt, Saudi Arabia and the United Arab Emirates.