US President-elect Donald Trump's reiteration of his opposition to the bid by Japan's Nippon Steel to acquire US Steel continues to draw mixed reactions.

United Steelworkers International President David McCall released a statement saying the union welcomes Trump's announcement.

It says, "it's clear that President Trump understands the vital role a strong domestic steel industry plays in our national security, as well as the importance of the jobs and communities the industry supports."

The Associated Press news agency reports that the mayor of a town in Pennsylvania, the state where US Steel is headquartered, has voiced support for the planned takeover.

West Mifflin Mayor Chris Kelly said at an event on Tuesday that there's no question in his mind that it's the best deal.

The US Committee on Foreign Investment has been reviewing Nippon Steel's bid to see if it poses any national security risks, ahead of a deadline later this month.

Nippon Steel said on Tuesday it believes the takeover will protect and help grow US Steel. It says it will reinforce the American industry, its supply chain resilience and US national security.

The Japanese company also said it plans to invest more than 2.7 billion dollars in US Steel.

It added that it promises to introduce top-class technology so American workers can provide the most advanced steel products to US customers while protecting employment there.