WASHINGTON (Reuters) - General Motors GM.N Chairman and Chief Executive Officer Mary Barra said her face-to-face session with U.S. President Donald Trump on Thursday was "productive and valuable," but declined to offer specifics.

General Motors Chief Executive Mary Barra departs after meeting with U.S. President Donald Trump at the White House in Washington, U.S., September 5, 2019. REUTERS/David Shepardson

The head of the largest U.S. automaker met with Trump days after the president stepped up attacks on the Detroit automaker. He has been slamming GM for much of the last year after the company announced in November it would end production at four U.S. plants and eliminate thousands of jobs.

Barra, accompanied by GM general counsel Craig Glidden, declined upon leaving the White House to say if she discussed the fate of the shuttered Lordstown, Ohio plant with Trump. GM has been in talks to sell the plant to EV startup Workhorse Group Inc and an affiliated, newly formed entity.

People briefed on the matter said Trump and Barra were expected to discuss ongoing contract talks with the United Auto Workers union, the fate of the closing plants, trade issues with China and North America and the Trump administration’s plan to rewrite fuel economy standards through 2026.

The White House declined to comment on the meeting.

Last Friday, Trump again criticized GM on Twitter saying the company “which was once the Giant of Detroit, is now one of the smallest auto manufacturers there.”

Last week, Trump suggested GM should begin moving operations back to the United States from China. “They moved major plants to China, BEFORE I CAME INTO OFFICE.... Now they should start moving back to America again?” Trump said on Twitter.

GM did not directly comment on Trump’s tweet last week but said its China operations “are not a threat to U.S. jobs.”

Trump has previously attacked GM for building vehicles in Mexico and for ending production at plants in Michigan, Ohio and Maryland. He has threatened to cut GM subsidies in retaliation and in June rejected a request to waive tariffs on Chinese-made Buick Envisions.

Trump has warned GM not to join Ford Motor Co F.N and three other automakers in backing a voluntary deal with California for stricter fuel economy standards than the administration has proposed. GM has not backed the agreement, arguing that it does not properly credit the company's electric vehicles.