European Union's plan to raise tariffs on imported steel are "extremely concerning" for Wales' steel industry, the Welsh government has said.
The commission has set out plans to cut the amount of steel that can be imported into the bloc by half - beyond which the new 50% tariffs will apply.
Alasdair McDiarmid, assistant general secretary of the Community union, warned that since about 80% of UK steel exports go to Europe, the move posed an "existential threat" to the industry and could devastate jobs and production.
The Welsh government said it would continue working with the UK government to protect the sector as Tata develops a new, greener steel plant in Port Talbot by 2027.
The EU is the UK's largest steel export market, worth nearly £3bn and making up 78% of steel products made in the UK for overseas markets.
The European Commission plans to cut tariff-free steel imports by 47% to 18.3 million tonnes a year, with the new measures set to come into force early next year pending approval by the majority of EU member states and the European Parliament.
It follows pressure from some member states and their steel industries, which have been struggling to compete with cheap imports from countries like China and Turkey.
This move could severely impact UK steelmakers, which rely heavily on EU trade.
Steel making at the Tata plant in Port Talbot shut down just over a year ago with the loss of more than 2,000 jobs.
However, the company, with £500m cash from the UK government, is investing £1.25bn in greener steel production and says a more environmentally friendly plant is expected by 2027.
It is hoped that the new electric arc furnace will reduce the site's carbon emissions by about 90% and will support 5,000 jobs.
Prime Minister Sir Keir Starmer said there would be "strong support" from the UK government for the British steel industry, which could be severely impacted by EU tariffs.
"I'll be able to tell you more in due course, but we are in discussions as you'd expect", Sir Keir Starmer said, refusing to go into the details of any discussion, including whether the UK was seeking exemptions from the rules.
A spokesperson for Welsh government said it remained "proud" of Wales' steel industry as "it is a fundamental part of our nation's future".
It said it will continue supporting workers through the shift to greener production "in all ways that we can".
The statement called the EU's announcement "extremely concerning" and pledged to work with the UK government to protect "skills" and "economic growth".