MADRID, June 16 (Reuters) - The new circuit for the Spanish Grand Prix, part of the Formula One World Championship, had a dazzling public opening ceremony on Tuesday, and organizers expressed confidence that everything would be ready for the race in Madrid in September, despite construction work not being completed.

The largest Spanish flag in the country was raised at the first turn, before government and circuit officials gave their speeches, and Williams driver Carlos Sainz spoke about the excitement he felt about racing in his hometown.

The 5.47-kilometer Madring circuit runs around the famous exhibition center in the northeast of the capital and is easily accessible by public transport and Barajas Airport.

"It's a track that has everything: fast parts and slow parts, an urban part and a more open part, it's really different," said Sainz, the track ambassador who has already driven the road-legal Ford Mustang GT.

Paving work is complete, but the maintenance area is still under construction.

While the black strip of smooth asphalt has been laid, the areas surrounding the circuit are crowded with excavation equipment, as hundreds of workers prepare the spectator stands, which will also host the largest fan zone of the championship.

Construction work on the maintenance corridor garages is still ongoing, the temporary grandstands have not yet been built, and the team assembly area is still in the design phase.

But Carlos Jimenez, operations manager at Madring, said he sleeps soundly, despite the tight deadlines and difficult obstacles.

He told Reuters, "We are in month 11 of construction work, and it took 12 months to get the licenses. Now the most difficult part has been completed; the circuit in the south has been finished. In the north, the plot of land will be finished within three weeks."

He added, "What we will begin, perhaps within two weeks, is the construction of temporary structures, bleachers, and hospitality facilities."

He confirmed that building these elements will take about a month and a half, but the high temperatures in July and August may force workers to stop working when temperatures reach their peak.

He said, "The workers may need to work during the night. So we have allocated a spare time and they can work night shifts because the building permit allows us to work 24 hours a day."

The FIA has conducted two inspection visits, and a third and final visit is scheduled for mid-August, during which the track will be sprayed with water to improve grip. The fan zone will be ready by the end of August, and Formula 3 cars will begin testing the circuit.

The circuit's electronic systems, including lighting panels and tunnel lighting, will be completed in July, as the circuit will pass under a highway that divides the area in two.

The deadline will be August 30, when the city council will inspect the facility.

The race, which is the second Spanish Grand Prix after the Barcelona-Catalunya Grand Prix held this month and the first to be held in Madrid since the Jarama circuit hosted Formula 1 races from 1968 to 1981, is scheduled to take place.