The chief executives of AT&T and Verizon Communications rejected a request to delay the planned January 5 introduction of new 5G wireless service over aviation safety concerns but offered to temporarily adopt new safeguards.

U.S. Transportation Secretary Pete Buttigieg and Federal Aviation Administration (FAA) chief Steve Dickson had asked AT&T CEO John Stankey and Verizon CEO Hans Vestberg late Friday for a commercial deployment delay of no more than two weeks.

The wireless companies in a joint letter on Sunday said they would not deploy 5G around airports for six months but rejected any broader limitation on using C-Band spectrum. They said the Transportation Department proposal would be "an irresponsible abdication of the operating control required to deploy world-class and globally competitive communications networks."

The aviation industry and FAA have raised concerns about potential interference of 5G with sensitive aircraft electronics like radio altimeters that could disrupt flights.

Read more: Airbus, Boeing 'concerned' over U.S. 5G instrument interference

The exclusion zone AT&T and Verizon propose is currently in use in France, the carriers said, "with slight adaptation" reflecting "modest technical differences in how C-band is being deployed."

"The laws of physics are the same in the United States and France," the CEOs wrote. "If U.S. airlines are permitted to operate flights every day in France, then the same operating conditions should allow them to do so in the United States."

The FAA said in a statement on Sunday that it was "reviewing the latest letter from the wireless companies on how to mitigate interference from 5G C-band transmissions. U.S. aviation safety standards will guide our next actions."

FAA officials said France uses spectrum for 5G that sits further away from spectrum used for radio altimeters and uses lower power levels for 5G than those authorized in the United States.

Verizon said it will initially only use spectrum in the same range as used in France, adding it will be a couple of years before it uses additional spectrum. The larger U.S. exclusion zone around U.S. airports is "to make up for the slight difference in power levels between the two nations," Verizon added.

Sara Nelson, president of the Association of Flight Attendants-CWA (AFA), representing 50,000 workers at 17 airlines, on Sunday wrote on Twitter that pilots, airlines, manufacturers and others "have NO incentive to delay 5G, other than SAFETY. What do they think… we're raising these issues over the holidays for, kicks?"

The Air Line Pilots Association also backed the delay.

Government and industry officials said the exclusion zones proposed by the wireless carriers are not as large as what has been sought by the FAA.

The FAA and Buttigieg on Friday proposed identifying priority airports "where a buffer zone would permit aviation operations to continue safely while the FAA completes its assessments of the interference potential."

Trade group Airlines for America, representing American Airlines, FedEx and other carriers, on Thursday asked the Federal Communications Commission (FCC) to halt deployment around many airports, warning thousands of flights could be disrupted daily.