Creating a humanitarian safe zone in Syria would entail a "major combat mission" requiring American troops to fight Islamist jihadists and the Damascus regime, Defense Secretary Ashton Carter told lawmakers on Wednesday, according to AFP.
Turkey has long called for a safe area to be set up along the Syrian-Turkish border to protect civilians but President Barack Obama's administration has yet to endorse the idea.
Carter emphasized the challenges involved in establishing a buffer zone, and warned that other regional governments might not be ready to contribute to the effort.
"We would need to fight to create such a space and then fight to keep such a space and that's why it's a difficult thing to contemplate," Carter told members of the Senate Appropriations defense subcommittee.
Carter was asked about the option by Senator Dick Durbin, one of four senators to send a recent letter to Obama calling for setting up a safe area in Syria.
"Though this may not be a genocide by classic legal definition, it is the humanitarian crisis of our time … with no end in sight," Durbin was quoted by AFP as having said.
Carter said such a safe zone would be "contested" by the Islamic State (ISIS) group and other extremists on the one hand and the Syrian regime's forces on the other.
The "practicalities" would be "significant," he said.
The U.S. military's top-ranking officer, General Martin Dempsey, said American commanders have drawn up contingency plans for a safe zone in consultation with their Turkish counterparts.
"We've been planning for such a contingency for some time," Dempsey told the same hearing.
He said American forces were capable of carving out a buffer zone in Syria but it was a major political decision and would mean troops stationed elsewhere would not be available for other missions.
"It's practical militarily but it would be a significant policy decision to do so," explained Dempsey.
He also said that for "this to be practical and effective, it would have to involve regional partners."
More than 215,000 people have been killed in Syria since the start of the civil war in March of 2011.
Syrian President Bashar Al-Assad said earlier on Wednesday that setbacks are a normal part of any war and do not mean the conflict is lost, in his first comments after several regime defeats.
"Today we are fighting a war, not a battle. War is not one battle, but a series of many battles," he said, adding, "We are not talking about tens or hundreds but thousands of battles and… it is the nature of battles for there to be advances and retreats, victories and losses, ups and downs."
The comments from Assad at an appearance at a Damascus school were his first since a string of regime losses, particularly in northwestern Idlib province.
In the last few weeks, rebel forces including Al-Qaeda's Syrian affiliate Al-Nusra Front have seized Idlib's provincial capital, the strategic town of Jisr al-Shughur, and a military base in the area.