Panasonic is cutting 15,000 jobs worldwide and closing 27 plants
Unions are calling on politicians to help them minimise the "massive impact" of planned job losses at Panasonic.
The company confirmed on Friday that 139 jobs at Newport and 70 in Cardiff were at risk as part of global cuts.
"We'll be working hard during the 90-day consultation period to reduce redundancies if at all possible," said Bryan Godsell of Unite the Union.
The assembly government said it was in touch with the company and would hold a meeting early next week.
Mr Godsell said the impact was "very significant and very distressing".
"If the redundancy takes place as proposed it will have a massive impact on the economy of south east Wales," he said.
"Once again we may see well paid highly-skilled jobs sacrificed at a time when the Welsh economy can ill afford further job losses.
"We will be working within the formal consultation process and calling on local politicians to work with us to minimise the impact of the redundancy proposal in order to secure and consolidate the future of Panasonic in Newport."
At the Newport plant, which employs 413 people making telephone systems, 139 jobs could go.
Meanwhile in Cardiff, 70 out of 640 workers could face redundancy.
The positions are all in the microwave oven division and other units are not affected.
Those really quality jobs with knowledge-based input, we don't want to see those going
Jonathan Deacon, Newport Business School
Mervyn Burnett, of the GMB union said: "This is very disappointing news.
"We are seeking an urgent meeting with the company to try and find out the nature of the problem."
Panasonic said aggressive competition, coupled with a reduction in demand and the "negative effects" of exchange rates were behind the restructuring at the Newport telecoms site.
Margins had been reduced so far, the company said, that the business would be difficult to sustain without changes to strategy.
It said the intention of the restructuring was to keep "a lean, highly skilled organisation capable of continuing the profitable, effective operation".
The cuts in Wales are part of a global attempt to reduce costs which will see 15,000 jobs lost and 27 plants closed.
Jenny Randerson, the Welsh Liberal Democrats' economy spokesperson said the company was "very precious" to Wales.
"It was an incomer at a time when there were very few. It has remained loyal to Wales... it's built up especially the high-end, high value-added jobs," said Ms Randerson, whose Cardiff Central constituency includes the plant.
Jonathan Deacon of Newport Business School said the cuts were another sign the recession was "digging yet deeper" into the Welsh economy.
"The announcement seems to focus around production of microwave ovens in Cardiff and we could see why that may happen - the global appetite for domestic appliances has dropped - but what we don't want to see are those really quality jobs with knowledge-based input, we don't want to see those going," he said.
A spokesperson for the assembly government said it was "very disappointing news".
"We have been in touch with the company and will be meeting them early next week to discuss the implications of this announcement and how we might be able to support them."
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