The Circuit of the Americas (COTA) has been hit by a funding cut, leading to doubts over the future of the United States Grand Prix.

The Texas track made its Formula 1 debut in 2012 and the first four editions have been a major success, but the event is facing uncertainty after the State of Texas announced a 20 percent reduction in funding.

The first three races received $25m per year, but it dropped to $19 million for this year's grand prix, leaving the circuit with a $6m shortfall on top of the reduction in ticket sales due to bad weather.

"To use a technical term, I think we're screwed," circuit chairman Bobby Epstein told the American-Statesman.

"It hit us cold. No one could foresee this coming. But the big question now is, 'Is the race coming back?'"

The state, which justifies the reduction in funding on grounds that the economic impact of the event on the area has dropped, could still face a court challenge from COTA.

"An entire facility was constructed based on that deal," COTA spokesperson Dave Shaw added. "If the calculation changes now, that's effectively changed the terms of the deal."

Formula 1 supremo Bernoe Ecclestone, who has recently revealed that he is hoping to add more American races to the calendar, admits Texas is up against it.

"If it's changed, it's going to be difficult to continue the race in Austin," he said.