"That is completely untrue. There will be 19 races," said a spokesman for the Formula One world champions on Thursday.

Rival team boss Frank Williams, asked about a report that Ferrari was privately threatening to boycott Magny-Cours and Silverstone, confirmed there was a problem over cash compensation.

"The teams have all agreed except Ferrari who want more money than some of the others," he told reporters after a sponsor news conference.

The calendar has been stretched to 19 races, more than ever before, with France and Britain securing their places at the last moment.

Although the expansion is subject to the agreement of all the teams, Williams played down the seriousness of the problem.

"I think at the end of the day (Formula One supremo) Bernie (Ecclestone) will sort something out," he said.

"Bernie can make things happen. There is a threat but I don't think it's significant."

A spokesman for the governing FIA said the issue had not been raised with them.