Washington, D.C. ? Al-Qaida terrorists may be plotting more urgently to attack the United States to maintain their credibility and ability to recruit followers, the U.S. military commander in charge of domestic defense said Thursday.

Air Force Gen. Gene Renuart, chief of the U.S. Northern Command, also told reporters he has not seen any direct threats tied to the U.S. presidential elections. But he said it would be rash to think that such threats are not there.

“We need only to look at Spain and see that they’re certainly willing to try to do something that is significant that could affect an election process,” Renuart said. “I think it would be imprudent of us to let down our guard believing that if there’s no credible threat that you know of today, there won’t be something tomorrow.”

While he said that U.S. authorities have thwarted attacks on a number of occasions, he said terrorist cells may be working harder than ever to plot high-impact events.