Washington ? The Transportation Department is not backing off a Dec. 31 deadline for mandatory screening of all checked baggage despite new warnings from airport officials that it will disrupt operations and could delay travel.

Officials from 39 airports, including Kansas City International, St. Louis’ Lambert Airport and Wichita Mid-Continent, wrote Transportation Secretary Norman Mineta last week asking him to pressure Congress to push back the deadline.

Mineta has maintained that while it will be difficult, several types of machines can be in place before 2003 to check an estimated 1 billion bags a year for explosives. The screening is required by an airline safety law passed after the Sept. 11 attacks.

“We’re not sure airports will be able to operate on Jan. 1,” said Larry Cox, chief executive of the airport in Memphis, Tenn. “It’s just not going to work unless we slow down and do it right.”

Russell Widmar, Kansas City’s aviation director, said he was concerned because no one from the Transportation Security Administration had visited his airport.

“We have seven months left to meet the deadline, and no one’s been here,” he said.

The letter warns about “harried installations” of explosives detection machines in airports that have little space for new equipment. The changes “promise to disrupt passenger flows and further increase the hassle of air travel,” the letter said.

Transportation Department spokesman Chet Lunner said Sunday that while Mineta understands concerns, he “is dead set about meeting the letter of the law, and we will.”

“The law doesn’t give us an option of relaxing the deadlines,” Lunner said.

The letter was signed by leaders of airports that handle a majority of the country’s air traffic, including Atlanta, Dallas, Denver, Detroit, Houston, Indianapolis, Las Vegas, Memphis, Metro Washington, Orlando, Phoenix, San Francisco and Charlotte, N.C.

Mineta has said that large, $1 million explosives detection equipment will be installed in some of the busiest airports, while other airports will have smaller, less expensive machines that can detect traces of explosives.