WASHINGTON, Oct. 24 (Xinhua) -- U.S. Transportation Secretary Sean Duffy said Friday that there is frustration and anxiety among air traffic controllers as the federal government shutdown drags on and the stress level they are under right now is "unacceptable."

At a press conference held at Philadelphia International Airport, Duffy said that controllers received about 90 percent of their pay roughly 10 days ago but will get no paycheck next Tuesday.

"If we don't have enough controllers, if we have controllers that are more stressed and less able to do the job, we pay close attention to that, and we will reduce the capacity of airplanes taking off and landing, or we will cancel flights," he said.

Duffy also noted that the system faces a shortage of about 2,000 to 3,000 air traffic controllers, and that efforts to close the gap will take a couple of years.

Starting this month, some 13,000 U.S. air traffic controllers have continued working without pay.

Nick Daniels, president of the National Air Traffic Controllers Association, said at the press conference that as the shutdown continues and air traffic controllers are not paid for the work they do, "that leads to an unnecessary distraction, and they cannot be 100 percent focused on their jobs, which makes this system less safe." ■