World Touring Car Championship will slash European dates in 2016

The calendar has already undergone substantial upheaval for 2015, with Qatar replacing Macau as the season finale, the Japanese date swapping from Suzuka to Motegi, and further new rounds at the Nurburgring Nordschleife, Vila Real and Thailand's Buriram circuit.

With the Salzburgring and Spa among the tracks dropped, that has left just six venues on the European continent: the Hungaroring, the Nurburgring, Slovakia Ring, Moscow Raceway, Paul Ricard and Vila Real.

"We will reduce even further the amount of WTCC events in Europe," said series boss Francois Ribeiro, speaking at a press conference ahead of the inaugural world championship race in Vila Real in Portugal.

"I think we can keep only four, maximum."

It is believed that the rounds in France and Slovakia are most likely to be axed, although Vila Real does not yet have a contract beyond this season.

Moscow Raceway represents a key market for Lada, independent frontrunner Norbert Michelisz draws great crowds to the Hungaroring, and the showpiece Nordschleife event is a labour of love for the series promoter.

"We can only keep events in Europe with very strong identity," said Ribeiro.

"Vila Real has a strong identity whether we like it or we dislike it...

"If the first event is good, if the mayor likes it, if his people like it, then normally we should be here for the next three years."

The dropped European races are most likely to be replaced by additional rounds in South America - possibly a street race in Santa Fe - and Asia.

These represent key developing markets for WTCC manufacturers.

Last week Citroen CEO Linda Carter told AUTOSPORT that her company would withdraw from either the WTCC or World Rally Championship in 2017, and that the decision would be influenced by those series' presence in key markets.