But those concerns seem to have fallen on deaf ears among several defense hawks in Congress.
Sens. John McCainJohn McCainPentagon should have a civilian chief to give peace a chance McCain to support waiver for Mattis, Trump team says Senators crafting bill to limit deportations under Trump MORE (R-Ariz.), Carl LevinCarl Levin'Nuclear option' for Supreme Court nominees will damage Senate McCain's Supreme Court strategy leads to nuclear Senate The Fed and a return to banking simplicity MORE (D-Mich.), Lindsey GrahamLindsey GrahamPentagon should have a civilian chief to give peace a chance Lawmakers eye early exit from Washington Senate passes college anti-Semitism bill MORE (R-S.C.) and Bob MenendezRobert MenendezThe right person for State Department is Rudy Giuliani Warren, Menendez question shakeup at Wells Fargo Democrats press Wells Fargo CEO for more answers on scandal MORE (D-N.J.) all want Obama to put military pressure on the Syrian regime by creating a no-fly zone and launching air strikes against the country's defenses.
Levin, the chairman of the Senate Armed Services Committee, said it was “essential” that the U.S. “step up the military pressure on the Assad regime.”
Dempsey reiterated the Pentagon's standing concerns on Wednesday.
"It will be difficult because the Syrian air defense system is sophisticated and it's dense," he said.
That said, "if that is a decision that the nation takes that we want to impose a no-fly zone, we'll make it happen," Dempsey added.
American military leaders have reportedly drafted strategic plans for a possible no-fly zone in Syria, located along the country's shared borders with Turkey and Jordan.
U.S. military advisers are working closely with the Jordanian military to address a number of regional security concerns, including Syria.
CIA operatives and U.S. special operations troops have also been training Syrian rebels in Turkey since late last year on using anti-tank and anti-aircraft weaponry, according to recent news reports.
Defense Secretary Chuck HagelChuck HagelLobbying World Ex-Dem leader: Clinton should include GOP in Cabinet Even Steven: How would a 50-50 Senate operate? MORE also recently approved a request from Amman to keep a detachment of Air Force F-16s and a Patriot anti-aircraft missile battery in Jordan.
Earlier this year, then-Defense Secretary Leon Panetta ordered a Patriot missile battery to be deployed along Turkey's border with Syria.