The United States might not have the legal authority or the military wherewithal to establish a series of no-fly zones along the Turkish-Syrian border, a top American diplomat said on Wednesday. 

Speaking to local media in Ankara, U.S. Ambassador to Turkey Francis Ricciardone said there were several serious hurdles the United States and its allies in the region needed to clear before standing up the no-fly zones. 

{mosads}”There are serious legal and practical obstacles on this issue,” Ricciardone reportedly told Turkish media outlets. 

American diplomats and their counterparts in Ankara will continue to “work on the subjects of a transition phase [in Syria] and buffer zone within the U.N. Security Council in line with international law,” he added.

His comments come as Pentagon and State Department officials work on a series of contingency plans for Syria, focused on addressing the myriad security and stability issues if President Bashar Assad falls. 

Secretary of State Hillary Clinton was in Istanbul negotiating the details of those plans with Turkish officials last weekend. 

Those plans have reportedly included consideration of using American and allied airpower to enforce no-fly zones in northern Syria along the Turkish border. 

Anti-Assad rebels have been slowly gaining ground in the north, concentrating their forces in the city of Aleppo. 

However, government troops loyal to the regime have been mercilessly hammering rebel positions inside Aleppo over the past few weeks, zeroing in on rebel strongholds with attack helicopters and fighter jets. 

Last Tuesday, White House counterterrorism chief John Brennan said U.S. policymakers have not ruled out creating the zones as part of the some sort of post-Assad contingency strategy for Syria. 

But on Wednesday, Ricciardone was quick to point out that no commitments have been made to support the zones, despite ongoing talks between U.S. officials and their allies. 

“Of course we should evaluate these issues. However, our discussions of these issues with Turkey should not suggest we are making commitments to set up these zones,” he said. 

Defense Secretary Leon Panetta and Chairman of the Joint Chiefs of Staff Gen. Martin Dempsey echoed those sentiments during a briefing at the Pentagon on Tuesday. 

“There is no question in my mind that we have positioned a sufficient force in the Middle East to deal with any contingency at this time,” Panetta said. “We’re prepared to be able to respond to whatever the president of the United States asks us to do.” 

Dempsey noted that both Turkey and Jordan “have examined the possibility of a safe haven” in northern Syria, via a no-fly zone. 

However, the four-star general was adamant the Pentagon was not planning any unilateral action to support a proposed safe haven in the country. 

“We plan for a number of contingencies and we have planned for a number of contingencies” in Syria, Panetta added. “With regards to the no-fly zone, that is not a front-burner issue for us.”