Thousands of people have taken part in a march calling on the government to help the Corus steel plant in Redcar which is faced with closure.
Up to 2,000 jobs at the Teesside Cast Products factory are at risk after an international consortium pulled out of a 10-year-deal to buy its steel.
Organisers said Saturday's "Save our Steel" event sent out a strong message.
The government said: "We are... engaged with Corus to try to secure the future for as many workers as possible."
Union organisers said up to 5,000 workers and their families had turned out for the march and rally.
Marchers included workers from the local port, and Teesside's chemical industry, as well from the Corus plants in Scunthorpe, North Lincolnshire, and Rotherham and Stocksbridge, South Yorkshire.
There was also a message of support from the Australian Workers' Union, which is fighting to save its steel jobs.
It was announced in May that the 150-year-old Redcar plant was to be mothballed, and progress in talks to resolve the contract problems has been hindered by a slump in demand for steel.
Unite, one of the unions active at the plant, said the Teesside community will be devastated if the Corus plant is shut down, as many local families and businesses depend on the plant for their livelihoods.
People came from all over the country to be here, and it tells us that we are not alone
Bob Stainthorpe, multi-union committee deputy chairman
Bob Stainthorpe deputy chairman of the multi-union committee at the plant, said up to 5,000 people were crammed the length of Redcar High Street.
"It just shows the public support we have," he said.
"People came from all over the country to be here, and it tells us that we are not alone."
Roy Rickhuss from the Community Union said: "We need help, we need support from the government if the manufacturing base in this country is going to survive.
"And steel is key to that, without steel there is no manufacturing base in this country."
However, Vera Baird, the MP for Redcar, said she was hopeful Corus would get the contract back.
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"There are other people who are interested in buying our steel now," she said.
"So I feel that although we are still in real peril, we do have a real prospect.
"And make no mistake, the government is 100% behind, and has played a key role in encouraging these negotiations to resume."
A Department for Business spokesman said: "We have offered £5m in training support to help the workforce up skill for the upturn, signalling a real commitment from the Government to Corus and its workforce.
"The difficulties that the company is facing are caused by an extreme downturn in demand for steel around the world.
"It is restructuring as it seeks to match production to lower demand and to position itself for to the future."
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