In a surprise and at times combative appearance at the White House press briefing, departing Transportation Secretary Ray LaHood painted a dismal picture of delayed flights, shuttered control towers and irate passengers from coast to coast if across-the-board spending cuts are allowed to take place under the process known as sequestration.

"Flights to major cities like New York, Chicago and San Francisco and others could experience delays of up to 90 minutes during peak hours," LaHood said. "Delays in these major airports will ripple across the country."

Automatic across-the-board budget cuts totaling $85 billion are set to take effect on March 1 unless Democrats and Republicans come to some agreement to stop or postpone them.

The White House and Democrats in Congress have been ratcheting up a public relations campaign to warn about potential job losses, cuts and disruptions in public services, all designed to prod constituents into pressuring Republicans into submission on the cuts.

Three Republican members of Congress who serve on committees with oversight over transportation called LaHood's assertion's "exaggerations."

The agency was "well positioned to absorb spending reductions without compromising the safety and efficiency" of the flight system, said a statement on Friday by Representative Bill Shuster of Pennsylvania, Senator John Thune of South Dakota and Representative Frank LoBiondo of New Jersey,

Republicans, who have argued that government over-spending is hurting the US economy, have so far rebuffed President Barack Obama's request for a delay. A number of Republican members of Congress have said that while the cuts may be painful, they could be a necessary jolt to wean the nation from excessive government spending.

A Pew Research Center poll on Thursday showed only modest public awareness of the cuts.

LaHood was the first Cabinet secretary brought to the briefing room recently as part of the White House effort.

Asked about that, he said: "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."

LaHood's briefing coincided with the release by his department of a list of smaller airports in congressional districts across the country that would have to curtail operations because of furloughs caused by the cuts.

After days of White House warnings that services like law enforcement and food safety inspections will suffer from the cuts, reporters challenged LaHood repeatedly.

One asked him how was it that air traffic controllers would be furloughed and more than 100 air traffic towers closed if only $1 billion of his department's $70 billion budget was at risk.

"Where I come from, which is central Illinois, a billion dollars is a lot of money, and it's very difficult when you have this kind of, the number of employees that we have guiding planes in and out of airports, to do anything except look at everything," he said.

LaHood's warnings did not worry some aviation experts. George Hamlin, president of Hamlin Transportation Consulting, said his comments "sound like scaremongering."

"This sounds like the proverbial 'The sky is falling' per Chicken Little," Hamlin said.

But LaHood and other administration officials deny they have any discretion in applying the cuts or that they are exaggerating their impact.

"The idea that we're just doing this to create some kind of a horrific scare tactic is nonsense," LaHood said. "We are required to cut a billion dollars. And if more than half of our employees are at the FAA (Federal Aviation Administration) ... there has to be some impact."