General Motors Co. says it will announce an investment in its Orion Assembly Plant on Friday after days of public pressure from President Donald Trump over the idling of its Lordstown Assembly Plant in Ohio.

The Detroit automaker plans to announce a "major new investment focused on the development of GM future technologies" during a 10 a.m. Friday press conference at the Orion plant, the company said in a media advisory.

The planned investment, which GM is not yet detailing publicly, would be the latest in a series of plant investments the company has made in recent weeks. The company is investing in plants even as it begins the process of idling five North American plants, including Lordstown Assembly in northeast Ohio, which stopped production on March 6.

The future of Lordstown, Detroit-Hamtramck Assembly, Warren Transmission and Baltimore Operations — all slated for "unallocation" — will be determined by GM and the UAW, which will negotiate a new national contract this summer.

Ford this week reiterated its commitment to invest $900 million in its Flat Rock Assembly Plant and add 900 jobs to build battery-electric vehicles.

Detroit carmakers again have seized the attention of the president, who ran for office on promises to revive American manufacturing. After three days of tweeting about GM and Lordstown, Trump again blasted the automaker and the United Auto Workers that represent its factory employees during a visit to a UAW-represented plant in Lima, Ohio.

Orion Assembly currently builds the Chevrolet Bolt EV and Sonic small car. It also assembles the GM Cruise LLC autonomous test vehicles, which are based on the Bolt.

As the result of a hefty incentive package from the State of Michigan, GM established Orion as its hub for small-car production in the United States just before the Detroit automaker emerged from bankruptcy. Most other manufacturers outsource small-car manufacturing to lower-cost countries like Mexico because the high cost of U.S. labor is difficult to justify on lower-margin vehicles.

nnaughton@detroitnews.com

Twitter: @NoraNaughton