Nissan has received complaints from owners that its Leaf electric car on occasion fails to start, posing a potential setback for the automaker's goal of promoting zero-emission vehicles.

Japan's No. 2 automaker said on Monday it was looking into the cause, which it traced back to the Leaf's air-conditioning unit.

Nissan is investigating whether the glitch was in a certain component or in the programming, spokesman Toshitake Inoshita said.

Nissan plans no recall for now since the issue does not affect safety, but will decide how to proceed after identifying the source of the problem, he said.

"When we know the exact cause, we will decide whether to issue a service bulletin, or take other steps," Inoshita said.

He added that the phenomenon was reported in both the United States and Japan, although he did not have an exact figure for the number of complaints.

Nissan and its French partner Renault are aiming to become leaders in the nascent field of electric vehicles, which plug into an electric outlet to power the car's batteries and have no tailpipe emissions.

Nissan launched the five-seater Leaf in Japan and the U.S. in December.

It sold more than 3,300 units in Japan as of February and delivered another 452 in the U.S. through March.