Plans by car giant Ford for a shake-up of its European operations could lead to the loss of 1,000 jobs at its site in Bridgend, unions have told ITV News.
It is understood the Bridgend engine plant will be the hardest hit of any of the firm's UK factories if the plans go ahead.
The company gave no details about job losses in the UK, but said it was starting consultations with unions to implement a "comprehensive transformation strategy".
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The First Minister said he is seeking an urgent meeting with Ford to discuss the plans.
Sources said the plans were for a total of 1,150 job losses in the UK, with almost 1,000 at Bridgend and the rest at Ford's transport operations, which would affect lorry drivers.
The plans are for two phases of cuts at Bridgend, achieved by 2021, sources said.
Ford declined to confirm the figures and said it was consulting with unions.
The company announced on Thursday that it would be speeding up plans to cut structural costs.
"We are taking decisive action to transform the Ford business in Europe," said Steven Armstrong, Ford's group vice president and president, Europe, Middle East and Africa.
"We will invest in the vehicles, services, segments and markets that best support a long-term sustainably profitable business, creating value for all our stakeholders and delivering emotive vehicles to our customers."
Assembly Member for Ogmore, Huw Irranca-Davies, said "new production in Bridgend" is needed to secure the plant.
Union Unite said the proposals are a "blow for our members and their families" and vowed to fight any compulsory redundancies.
It said shop stewards from Ford factories have been given a briefing on the proposals and they will be "campaigning strongly for Bridgend to have a viable future.:
Ford said it was starting formal consultation with its works council and trade unions, adding that it was committed to working with its key stakeholders over the new strategy.
The announcement from Ford came on the same day as Jaguar Land Rover said it was axing 4,500 jobs and Honda said it was halting production for six days after Brexit.
"Today's media reports regarding the Ford engine plant in Bridgend are deeply concerning.
"Ford is a significant employer across Ogmore and we know what a distressing time this will be for the workers, their families and the wider community.
"We are in regular communication with Ford's management in Bridgend and are keen to help provide as much certainty as possible at the earliest possible opportunity.
"We are pleased that the Welsh Government are taking a proactive approach to help protect the many highly skilled jobs in Bridgend and to secure a sustainable future for the plant. We will continue to assist them with this work in any way that we can.
"As soon as we have any updates with regards to the situation, we will of course share this information with you. Please do not hesitate to get in touch with us if you have any queries in the meantime."
Jeff Beck from the GMB Union told ITV News the union has been told 990 jobs will be cut at the site. "Everyone will suffer - it's awful for the area and for the whole of south Wales", he said.
The Welsh Conservatives said the news is a "real punch in the stomach to so many families."