Chicago officials were waiting Tuesday for approval from the Federal Aviation Administration to implement tighter security measures at O'Hare and Midway

airports in the wake of reports that terrorists had obtained detailed maps of O'Hare cargo facilities.

Published reports indicated that agents of Hamas, the Islamic fundamentalist group, had been observed at O'Hare, the nation's busiest airport, within the past three months.Hamas has threatened terrorist reprisals in New York in connection with the prosecution of those accused of the 1993 World Trade Center bombing and the pending extradition to Israel of arrested Hamas leader Mousa Abu Marzuk.

"They're terrorists, they've killed before, they know what they're doing, and it's good common sense to heighten security," the Chicago Tribune quoted one city official as saying.

The FBI has previously linked Hamas to a bomb factory in the Philippines in which several suspects escaped with triggering devices to detonate bombs in airplanes.

Alison Duquette, an FAA spokeswoman, while neither confirming nor denying that the agency had received a specific request to upgrade security at O'Hare, said, "The FAA works with airports to adjust the varying levels of security. Obviously we take any requests for adjustments seriously."

Lisa Howard, a spokeswoman for Chicago's Department of Aviation, which runs both O'Hare and Midway, said city officials had met with carriers and urged them "to beef up their own security, while assuring them that we had increased our security."

She also said that O'Hare security has been in excess of FAA "Level 2" since the Hamas threat was revealed to officials last week. But she declined to give details about security measures.

The FAA raised security measures at most airports around the country last Wednesday to Level 2. Last Saturday, it lifted them to Level 4, their highest level of security, at New York area airports.

Peter Yerkes, a spokesman for the Port Authority of New York & New Jersey, which operates JFK, Newark and LaGuardia airports, said it has elevated security in cargo at all three facilities. "Those measures are in addition to the steps we've taken in passenger areas," he said.

Like FAA officials, he declined to discuss specific measures, saying it would compromise security.

"We continue to analyze information provided by law enforcement and intelligence agencies," said Hank Price, another FAA spokesman, adding that the agency is preparing an advisory to freight forwarders recommending that they review their security procedures to ensure strict compliance with FAA regulations.

Mr. Price said the agency believes its recently revised standards are adequate to counter the potential terrorist threat.

Courier services at John F. Kennedy International Airport in New York were coping with heightened security procedures imposed over the weekend.

"At JFK, it's always been a problem leaving vehicles at curbside and now more so, so they're parking in the airport lots," said David Horn, general manager for Trans America Courier Systems Inc. of Woodside, N.Y.

Mr. Horn said parking in the lots may cost his company $300 to $400 a week, but he's willing to put up with it in the name of security.

Mr. Horn and other truckers said the measures were strict even before this latest warning. Drivers were required to ask for two pieces of picture identification and open packages from any unknown shipper.

The latest measures affect packages being given to airlines at the gate area. Some drivers are having a bit more trouble getting through increased security there.

John Lunn, director of air freight for Phoenix International Freight Services Ltd., a Chicago-based forwarder, said it had received no specific instructions from either the airlines or the FAA about changes in procedures.

Some trucking companies, however, were telling shippers they will need an extra 30 minutes before flight time to deal with possible delays.

But in most cases, the new procedures have had little effect on cargo movements.

"There is absolutely no impact on either cargo or priority parcels," said Ed Martelle, a spokesman for American Airlines, adding that small packages delivered by courier services to airline ticket counters are routinely X- rayed.

Tim Kilraine, operations manager for Adcom Express Worldwide, a Washington- based freight forwarder, said it had not yet experienced any delays, but that he has told his drivers "to be more on the alert and to keep their eyes open for anything suspicious or placed in trucks that doesn't belong there."

Giorgio Laccona, vice president for operations at Air Express International, a Darien, Conn., forwarder, said the air cargo industry has been acting under tighter security rules for more than a year. Freight from shippers who have not previously dealt with forwarders is subject to a 48-hour delay and can be inspected physically.

"We routinely open packages (from unknown shippers) and check the contents," said Mr. Kilraine.

FAA inspectors posing as unknown shippers have tested security procedures at several Adcom offices over the past year, he added.

"The cargo area is as tight as it has ever been. I can't say it's any tighter," said Donald Harrow, president of Personalized Pick-up Service of Des Plaines, Ill., which serves O'Hare Airport.

Stephen Alterman, president of the Air Freight Association, a Washington- based trade group representing all-cargo carriers, said the FAA measures are aimed primarily at passenger airlines. But, he added, "We're watching carefully everything we do."