LOS ANGELES -- BMW may have to increase production of its i8 plug-in hybrid sports car to meet high demand.

The waiting time for the 120,000 euro coupe is up to 18 months, BMW sales and marketing chief Ian Robertson said.

"We need to find ways to increase i8 production because the waiting lists in some markets are getting too long,” Robertson told Automotive News Europe at the auto show here on Wednesday.

Robertson said six months is as long as customers should have to wait for a built-to-order premium model.

The i8 is produced at BMW's factory in Leipzig, Germany. The car went on sale in Europe in June and in the U.S. in August.

Robertson declined to elaborate on current production levels of the i8, as well as on any potential output increase. He said BMW planned the i8 as a low-volume model with annual sales in the low single digit thousands.

So far this year BMW delivered to 760 i8 cars to customers including 419 in October.

IHS Automotive forecasts that BMW will build 3,238 units of the i8 this year, increasing to 4,318 next year.

i3, i5

Robertson said waiting time for the i3 battery-powered compact hatchback, which is also built in Leipzig, is stabilizing at about four to five months.

“We are now delivering about 2,000 units of the i3 a month,” he said. Through October, BMW delivered 12,184 units of the i3 worldwide, including 1,985 in October.

Asked whether BMW will launch a fuel call car called the i5, as media reports have suggested, Robertson said he was not aware of such plans. BMW is discussing how its 'i' range will evolve but no decisions have been made, he said.