(Reuters) - Toyota Motor North America said on Tuesday it had built extra inventory of vehicles and parts ahead of the U.S. port strikes, which began earlier in the day.

Toyota ( TM ), which relies on the U.S. East Coast and Gulf Coast ports to import everything from vehicle components to fully-built cars, said it was closely monitoring the situation.

Dockworkers on these coasts began a strike, their first large-scale stoppage in nearly 50 years, after negotiations for a new labor contract broke down.

"We built up some extra stock here over the last couple of weeks to help us buy a couple of days' worth of inventory," said Jack Hollis, chief operating officer at Toyota's ( TM ) North American unit.

The company had plans that it could implement to change ports and locations, Hollis said.

"It would just be crippling to the economy if this goes on for too long," he added.

The company also reported a decline of about 8% in its third-quarter sales of new vehicles in the United States, owing to three fewer selling days this year and cash-conscious buyers bogged down by inflationary headwinds.

Overall sales in the quarter fell to 542,872 units from a year earlier.