"I'm not sure how to make a call like that," Clapper replied.
"It would be very, very situational dependent," he added, "to render an assessment on how well we could secure any or all of the [weapons] facilities in Syria."
Washington would also need to generate sizable international support from its allies in the region and elsewhere to be able to mount a full-on security mission on those weapons, the Intelligence chief added.
"All those factors would have to be considered, certainly our own capabilities and what other capabilities could be brought to bear in the international community," he said.
Securing Syria's weapons stockpiles is a major concern for the Pentagon and intelligence community since Assad threatened to use those arms against rebels fighting to overthrow the longtime leader.
The Pentagon was reportedly drafting contingency plans to take out Syria's chemical weapons stockpiles until recent intelligence showed the country was backing off its efforts to use such weapons against rebel positions.
But with Damascus losing ground to Syrian rebels in the two-year civil war, concerns are rising these weapons could end up in the hands of Islamic extremists fighting alongside anti-government forces.
U.S. national security leaders are also looking to avoid a repeat of the situation in Libya, where American and NATO forces were unprepared to secure Libya's stockpiles of shoulder-fired rockets after former Libyan dictator Moammar Gadhafi was killed last March.
Shortly after Ghadafi's death, U.S. intelligence allegedly picked up "worrying indicators" that the missiles, similar to the famous Stinger anti-aircraft missile that the United States supplied to the Afghans to defeat the Soviets, had made their way to terror groups operating in the region.