660,000-square-foot air hub, which operates 20-22 hours a day at the San Bernardino International Airport, processes at least 18,000 shipments an hour and sends them out via airplanes and trucks as part of a sophisticated network aimed at satisfying customers’ online orders as quickly as possible.

According to the Teamsters, Amazon has until Sunday to set dates for negotiating a union contract. Hards disputed that.

“For more than a year now, the Teamsters have continued to mislead our employees, partners and the public — claiming we have an obligation to bargain with them,” Hards said. “We don’t.

“And because of their track record of misrepresenting the facts, we’re skeptical that their claims here are accurate or that they’ve gathered the required number of legitimate signatures to support their claim,” Hards said.

Randy Korgan, director of the Teamsters’ Amazon Division, said Amazon does not “seem to respect any set of rules when it comes to what workers’ rights are.”

Korgan noted that Amazon is arguing in court that the National Labor Relations Board’s structure is unconstitutional.

“Clearly, Amazon is ignoring everything and saying, ‘We did nothing wrong anywhere, anyhow and everybody else is wrong and everybody else’s iteration of this situation is incorrect,’ ” he said.

Hards said Amazon believes the labor board “is acting beyond its mandate, including by having its members serving as both prosecutors and judges on the same case.”

“This is a clear violation of separation of powers, and furthermore, they feel emboldened to do so because they are unconstitutionally insulated from removal,” Hards said.

Efforts to unionize air hub workers officially launched in November. In recent years, workers have complained about being cheated out of overtime pay as they toil in what they call sweltering conditions at breakneck paces that they say make them vulnerable to injury.

Amazon disputes those assertions and insists it prioritizes workers’ safety while offering robust pay and benefits and opportunities for employees to advance their education.

In July, air hub workers walked off the job and picketed outside the facility as part of a one-day strike over alleged unfair labor practices.

According to the Teamsters, air hub workers in September “marched on the boss and successfully shut down operations with full pay until conditions improved” when wildfires “caused intense heat and dangerous fumes at their facility and Amazon refused to safeguard their health.”

The air hub joins a list of Amazon facilities in California and nationwide where at least some workers are trying to unionize. The Teamsters said it formed unions with Amazon workers in San Francisco; Victorville; the City of Industry; Queens, New York; and Atlanta.

Workers at Amazon’s John F. Kennedy International Airport facility in New York City voted to affiliate with the Teamsters in June, and in August, a judge ruled Amazon must bargain with the Teamsters on behalf of Amazon drivers in Palmdale, the Teamsters said.