DUBAI (Reuters) -The United States intends to move forward with the sale of 50 F-35 stealth fighters jets to the United Arab Emirates but there must be a clear understanding of “Emirati obligations,” a U.S. official said on Tuesday as progress on the sale slows.

“We continue consulting with Emirati officials to ensure we have unmistakeable, clear mutually understanding with respect to Emirati obligations and actions before, during and after delivery,” said Mira Resnick a deputy U.S. assistant secretary of state, on a call with reporters, without elaborating on what the obligations were.

The sale of 50 F-35 warplanes to the UAE has slowed amid concerns in Washington over Abu Dhabi’s relationship with China, including use of Huawei 5G technology in the country.

“Washington continues to press Abu Dhabi on specific commitments regarding how and where the system will be operated once delivered, some of which might be viewed by the UAE as an infringement on its sovereignty,” the head of the U.S.-UAE Business Council, Danny Sebright, told Reuters.

“Chinese involvement (in) the UAE’s next generation of communications and data networks, China’s presence at UAE naval ports, and China’s offer of certain sensitive military technologies to the UAE are also significant sticking points complicating closure of the F-35 deal with the U.S.”

The United States under then-President Donald Trump agreed to sell the warplane after the UAE last year established ties with Israel. President Joe Biden’s administration has said this year it would proceed with the sale.

(Reporting by Alexander CornwellEditing by Peter Graff and Jonathan Oatis)