(Corrects airport that a passenger, Claudia Hartono, arrived at to Atlanta from Chicago's O'Hare in 10th paragraph)
* Napolitano says some long lines in Chicago, LA, Atlanta
* Passengers report no change in airport wait times
* Furloughs begin going out at TSA on Monday
* Customs checkpoints affected, furloughs later this week
WASHINGTON, March 4 (Reuters) - U.S. 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 and Customs and Border Protection will send them out later this week.
Hiring freezes for both agencies 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. Customs and Border Protection said in a statement on Monday that the agency had begun reducing overtime over the weekend and effects were already visible.
"Lanes that would have previously been open due to overtime staffing were closed, further exacerbating wait times at airports with typically longer international arrival processes," the statement said, noting that additional effects were expected in the coming weeks as furloughs - which will go out on March 7 - take effect.
However, the TSA website did not show any major delays at any U.S. airport on Monday morning. Karen Pride, a spokeswoman for the Chicago Department of Aviation, said flight operations out of Chicago's O'Hare International and Midway airports were normal on Monday.
Passengers said that lines for security on outgoing flights, and customs control for incoming flights, were not any longer than usual.
"Going through customs was normal. For me it took five to ten minutes," said Claudia Hartono, arriving in Atlanta from Indonesia.
At Hartsfield-Jackson Atlanta International Airport's main terminals, the wait was less than ten minutes. "It's the same as always," said Steve Brodie, 60, waiting to catch a flight to Florida.
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.
The cuts at the agency will be on the investigative side which handles financial and identity theft, cyber crime and counterfeiting cases. (Reporting by Deborah Charles; Additional reporting by James B. Kelleher in Chicago, David Beasley from Atlanta, and Atossa Araxia Abrahamian from New York; Editing by Jackie Frank)