New Jersey Gov. Chris Christie has told the Port Authority of New York and New Jersey to reject any flight routes between Newark and Cuba until a woman convicted of killing a state trooper is extradited to the U.S. – though one airline says it plans to push ahead anyway. 

The Republican governor and presidential candidate sent a letter to the bistate agency Tuesday urging them to reject any regular flight routes between Newark Liberty International Airport and Cuba until Joanne Chesimard, also known as Assata Shakur, is returned to the U.S.

"It is unacceptable to me as Governor to have any flights between New Jersey and Cuba until and unless convicted cop-killer and escaped fugitive Joanne Chesimard is returned to New Jersey to face justice," Christie wrote in the letter obtained by The Associated Press.

"I will not tolerate rewarding the Cuban government for continuing to harbor a fugitive," he said.

Chesimard was convicted in 1977 in the death of Trooper Werner Foerster during a gunfight after being stopped on the New Jersey Turnpike in 1973; she was sentenced to life in prison but escaped and made her way to Cuba, where Fidel Castro granted her asylum.

United Airlines has expressed interest in launching flight service from Newark to Cuba, as the U.S. continues to loosen travel restrictions as part of an effort to normalize relations between the two nations.

United seemed undeterred by Christie's objections.

United spokesman Rahsaan Johnson told The Associated Press that the airline intends to request the flights once an agreement is reached between the two nations under which airlines can apply to begin commercial air service. Asked about Christie's letter, Johnson said, "We remain very interested in serving Cuba as soon as we are able to do so, and believe United's service would benefit the airport and the region."

"I understand Gov. Christie's strongly expressed concerns and will commence an immediate review of the agency's role in the proposed flight between Newark and Cuba," "Port Authority Chairman John Degnan said. "I expect that review will be completed in a matter of days."

Christie has been a vocal critic of improved relations between the U.S. and Cuba, especially the Obama administration's decision to formally remove Cuba from a U.S. terrorism blacklist.

Meanwhile, United's relationship with the Port Authority has come under scrutiny from federal investigators amid allegations that the airline resumed a money-losing flight from Newark to South Carolina, near where the Port Authority's former chairman had a vacation home, at the same time United was pressing for concessions from the agency, including a new hangar at the Newark airport.

The flights were discontinued several days after Port Authority chairman David Samson stepped down in late March 2014.

The Associated Press contributed to this report.