TOKYO, May 22 (Reuters) - A slowdown in the take-up of electric vehicles in the U.S. may prompt Tesla-supplier Panasonic to delay investing in additional plants to boost its automotive battery capacity in North America, the Japanese group's chief executive said.

Panasonic, whose energy unit makes batteries for Tesla , is closely watching its Chinese supply chain and battery material procurement following China's move last year to tighten graphite export controls, Yuki Kusumi said.

"There's a need to control the speed of investment depending on the speed at which EVs spread," he said during a roundtable interview with reporters in Tokyo on Tuesday.

Kusumi's remarks may suggest Panasonic will not build a third battery plant in North America with its energy unit any time soon. It would probably take a while for the company to make a decision, Kusumi said.

Panasonic Energy has a battery factory in the U.S. State of Nevada and is building a second one in Kansas, as part of a push to expand annual battery capacity to 200 gigawatt hours by March 2031.

The company will decide investments based on commitments it gets from automakers, Kusumi said, adding that it was assessing mid- to long-term market demand.

"The one situation that should be avoided most, is one where a line is not used after making an investment," he said.

The transition to EVs from cars running on gasoline has hit a rough patch globally as consumers slow the pace at which they switch to battery-powered vehicles amid inadequate infrastructure in some developed markets.

Despite that trend, Chinese automakers including BYD are bringing lower-cost electric models that often use relatively cheap lithium iron phosphate batteries to a growing number of markets around the world.

Panasonic has seen a "drastic" decrease in demand for batteries for a certain car brand, pushing up fixed costs in Japan, Kusumi said, without naming the particular automaker or model to which it supplies batteries.

(Reporting by Daniel Leussink, Ritsuko Shimizu and David Dolan; Editing by Susan Fenton)