General Motors chief executive Mary Barra has vowed to keep an "open mind" about the future of an Ohio plant that will lose vehicle production, but warned the Detroit automaker has excess capacity and did not suggest the company was reconsidering the plan, a media report said.

Reuters said Barra came under pressure from Ohio's two US senators and other lawmakers who want GM to shift production of a vehicle from Mexico or build electric vehicles at the Lordstown Assembly plant in their state that the automaker has said it intends to close.

"I want to make sure that the workforce knows there are limitations and we do have an overcapacity across the country," Barra said, urging workers at plants set to close to take seriously offers of GM jobs in other parts of the country.

In a brief Reuters interview after her meetings Wednesday, she said it would be "very costly" to shift production from Mexico of the Chevrolet Blazer due to be launched in the next few days.

The news agency noted US president Donald Trump told GM last week that the company had "better" find a new vehicle to build at the plant in Ohio, which could be crucial to his re-election chances in 2020.

Asked about Trump's comments, Barra did not directly answer but said she understood the strong reaction in Washington.

"I understand this is something that impacts the country and I understand that there is a lot of emotion and concern about it," Barra said.

GM said last week it would close five North American assembly plants next year and cut up to 15,000 jobs as it blames slow selling car sales for the need to restructure.

The CEO said GM planned to add other products at US plants next year and that the automaker would have some jobs to fill at other Ohio facilities in 2019.

She cast the decision as critical to keep GM competitive. In the interview, she said GM wanted to "do the right thing for our employees but also make sure General Motors is strong and lean in the future".

Senator Rob Portman said Barra made no promises about the future of the Lordstown plant in Ohio where the soon-to-be-discontinued Chevrolet Cruze sedans are manufactured.

Barra said the plant's ultimate status will be determined during contract talks next year with the United Auto Workers (UAW) union.

"We're not asking for charity." Portman said, adding the members are asking for a new product for the plant to build.

Portman said he spoke to fellow Republican Trump on Wednesday about GM.

Reuters noted Barra was in Washington for meetings with lawmakers, including Senate Democratic leader Chuck Schumer as well as lawmakers from Ohio and Maryland. She was also expected to meet with lawmakers from Michigan on Thursday, among other meetings. After GM announced its plans, Trump threatened to eliminate subsidies for GM in retaliation.

Administration officials later said they wanted to end subsidies for electric cars in 2020 or 2021, affecting GM and other automakers.

Trump also said new auto tariffs were being studied, asserting, without evidence, that they could prevent job cuts such as those planned by GM.

According to Reuters, the UAW has objected to GM's plan to end production in 2019 at four US plants, saying it violates commitments made during contract talks in 2015. The union has asked GM to rescind the decision and resolve the fate of the plants in talks for a new labour contract next year.