* Napolitano says some long lines in Chicago, LA, Atlanta
* Furloughs begin going out at TSA on Monday
* Customs checkpoints also affected
WASHINGTON, March 4 (Reuters) - Secretary of Homeland Security Janet Napolitano on Monday cautioned airline passengers to get to the airport extra early because U.S. spending cuts have already led to long lines at some security checkpoints, and said the coming furloughs will only make the situation worse.
Napolitano said mandatory spending cuts ordered on Friday by President Barack Obama have led to the elimination of overtime for Transportation Security Administration officers and customs agents. She said TSA would begin sending out furlough notices to employees on Monday. Hiring freezes have also prevented any open positions from being filled.
"We are already seeing the effects at some of the ports of entry - at the big airports, for example. Some of them had very long lines this weekend," Napolitano said at a "Politico Playbook" breakfast event.
She pointed to Chicago's O'Hare International Airport, Los Angeles International Airport and Hartsfield-Jackson Atlanta International Airport as examples of those with long lines.
Napolitano said delays were between 150 percent and 200 percent at certain airports, although the TSA website did not show any major delays at any U.S. airport on Monday morning.
Some lawmakers have accused Napolitano and other administration officials of fear-mongering and exaggerating the impact that would be seen from the deep spending reductions known as the "sequester" which cut a total of $85 billion from government agencies between March 1 and Oct. 1.
But Napolitano said the problems were real.
"Look, people, I don't mean to scare, I mean to inform. If you're traveling, get to the airport earlier than you otherwise would," she said. "And please don't yell at the Customs officers or the TSA officers - they are not responsible for the sequester."
Napolitano did not give details on who at TSA would be furloughed and officials at the Department of Homeland Security did not immediately respond to requests for further explanation.
The Secret Service, which is also part of DHS, will see a five percent cut in spending but Napolitano said it would not impact security of the president.