WASHINGTON (REUTERS) - US President-elect Donald Trump on Tuesday (Jan 3) blasted US carmaker General Motors Co and threatened to impose a "big border tax" for making some of its Chevrolet Cruze cars in Mexico.

"General Motors is sending Mexican made model of Chevy Cruze to U.S. car dealers-tax free across border. Make in U.S.A. or pay big border tax!" Trump said in a post on Twitter.

Shares of GM fell about 1 per cent in premarket trading after Trump's tweet.

Representatives for GM could not be reached immediately for comment.

In November, GM said it planned in early 2017 to lay off 2,000 employees at two US auto plants, including one in Lordstown, Ohio, where it builds the compact Chevrolet Cruze.

GM had planned to build the Cruze hatchback in Mexico while continuing to build the Cruze sedan in Ohio, supplier sources have said.

The shift is part of a larger trend among Detroit's Big Three automakers to produce more small cars for the North American market in Mexico in an effort to lower labour costs, while using higher-paid US workers to build more profitable trucks, sport utility vehicles and luxury cars.