Charles Dharapak/AP Photo

Transportation Secretary Ray LaHood warned today that looming across-the-board spending cuts would cause flight delays at major airports, force the Federal Aviation Administration to furlough workers and have a "very serious impact" on the nation's transportation services.

Painting a bleak picture, LaHood told reporters "it's going to be very painful for the flying public" if the cuts kick in at the end of the month.

Overall, the Department of Transportation would need to cut roughly $1 billion from its $74.2 billion budget, less than 2 percent. More than $600 million of the cuts would come from the FAA, which would be forced to furlough the majority of its nearly 47,000 employees.

As a result, travelers could expect delays of up to 90 minutes at major airports like New York, Chicago and San Francisco because there would be fewer controllers on staff and some flight towers at smaller airports could close temporarily.

"You've got a big budget. Can't you find some other way to cut that without telling air traffic controllers to stay home?" ABC News' Jonathan Karl asked.

"That's a lot of money, Jonathan," the secretary, a Republican, replied.

LaHood's surprise appearance at the daily briefing comes as the White House is trying to ramp up pressure on Republicans to reach a deal to avoid so-called sequestration.

"I would describe my presence here with one word: Republican. They're hoping that maybe I can influence some of the people in my own party," the former Illinois congressman admitted.

LaHood urged his former colleagues in the Republican Party to "step up" and compromise and recommended they see the movie "Lincoln" for inspiration. "What Lincoln did is he gathered people around him the way that I believe president Obama is doing, by calling Republicans, talking to them, trying to work with them. And when that happens, big things get solved," he said.

LaHood, 67, cautioned lawmakers to expect a flood of calls from their constituents if air-traffic delays occur. "Why does this have to happen?" he asked. "Nobody likes a delay. Nobody likes waiting in line. None of us do.

"If we can't get our hamburger within five minutes, if we can't get on the plane within 30, 40, 50 minutes after going through, you know what happens. They start calling their member of Congress."