Wait times at Transportation Security Administration (TSA) checkpoints at major U.S. airports have already nearly doubled since sequestration was implemented, Homeland Security Secretary Janet Napolitano said on Monday.

Napolitano said Monday that the $85 billion in across-the-board spending cuts that were officially enacted last Friday have already resulted in airport security lines that are "150 to 200 percent" longer than they normally are.

"Now that we are having to reduce or eliminate basically overtime both for TSA and for customs, now that we have instituted a hiring freeze … we will begin today sending out furlough notices,” Napolitano said at an event that was sponsored by Politico.