"Everyone knows the costs for farmers will be high, and that national solidarity should come into play," Gaymard told the private Europe 1 radio station, assuring farmers the government would help them with cash flow problems.

"I can't give you a precise figure for the economic losses, but I'd say several billion euros... between one and four billion," the minister said.

Separately, the head of the main farmers' union in France estimated the total loss of production at four billion euros.

"To date, the losses in terms of sales are around four billion euros," said Jean-Michel Lemetayer of the FNSEA union, in an interview with the newspaper La Tribune.

"The total losses, however, are impossible to evaluate," he added.

The main setback to French farming this year has been an exceptional early August heatwave, which caused many crops to wilt and forced livestock farmers to use up forage intended for winter to feed their animals.

TERRA.WIRE