Panetta made the remarks at a NATO meeting of defense ministers. The revelation comes at a time of growing fears that the chaos and bloodshed in Syria for more than a year and a half could spread beyond the country across the Middle East.
Turkey has retaliated against Syria after repeated attacks on its territory, including shelling last week that killed five people. Though Turkey has said it does not want war, the two countries have continued to trade fire this week.
In Jordan, the enduring conflict has ramped up fears over the fate of Syrian chemical weapons and pushed more than 100,000 refugees into the country as winter approaches.
Defense spokesman Lt. Col. Jack Miller said in an email that the exact number of troops was “an issue we don’t want to get into,” but that the U.S. had been working closely with Jordan “on a variety of issues related to Syria for some time now,” including the refugees.
The number of refugees who have left Syria for Jordan is expected to swell to 250,000 by the end of the year, according to the United Nations. The U.S. has provided medical kits, water tanks and other humanitarian aid to help Jordan care for refugees, Miller wrote.
The allies are also eyeing the security of chemical and biological weapons stockpiled by Syria, a threat that President Obama has warned could change the tack toward the continuing conflict. If the Syrian government unleashes those weapons, Obama said, that would be a "red line" triggering U.S. military intervention.
The New York Times reported on the operation Tuesday, citing American officials familiar with the operation who said the force consisted of more than 150 planners and other specialists and was based north of Amman. An unnamed senior U.S. defense official cited the same number to the Agence France-Presse.
In a statement that appeared to anticipate questions about why the operation was revealed now, Miller wrote that the Department of Defense’s willingness to publicly discuss any deployment was based on agreements between those deployed and the host nation.
-- Emily Alpert in Los Angeles
Photo: U.S. Defense Secretary Leon Panetta talks to the media after a meeting of NATO defense ministers at the NATO headquarters in Brussels on Wednesday. Credit: Thierry Charlier / Agence France-Presse / Getty Images