MEXICO CITY, April 5 (Reuters) -

SAT Aero Holdings, a U.S. aviation firm hired by Mexico to

relaunch state-run airline Mexicana, was accused by President

Andres Manuel Lopez Obrador on Friday of breaching its contract,

after SAT made similar charges in a lawsuit against the carrier.

SAT is seeking at least $841 million in the

lawsuit filed last month, alleging that Mexicana reneged on

its obligations almost from the start.

According to SAT, Mexicana officials failed to pay $5.5

million of aircraft lease deposits, refused to sign documents,

went around SAT to directly hire pilots and crew trained by the

aviation firm, and failed to obtain licenses needed to import

planes to Mexico and operate them.

However, Lopez Obrador said it was SAT that "breached

the contract it had signed with Mexicana."

"They aren't serious people. They had agreed to deliver

the planes by a certain date and they didn't," he said at a

press conference.

Lopez Obrador

launched Mexicana last year

by reviving the brand of a bankrupt carrier, putting it in

the hands of the military.

The lawsuit said Mexicana had tasked SAT with obtaining

10 Boeing 737-800 aircraft ahead of its launch, which was

ultimately pushed back to December.

SAT alleged that Mexicana officials "continually cut the

financial legs out from under SAT and its own actions prevented

SAT from delivering the planes," while Mexican generals even

"threatened" SAT into signing an amendment to the contract.

Mexicana is operating with three Boeing ( BA ) planes from the

military and two Embraer ( ERJ ) aircraft rented from a

regional carrier.