The clothing label firm Burberry has agreed to delay by three months the closure of its factory in Treorchy.
The Burberry factory was set to close by the end of the year
The firm had planned to shut the south Wales plant, which makes polo shirts, at the end of the year with the loss of around 300 jobs.
Following a meeting with union leaders, the company has extended the closure deadline until 31 March next year.
Burberry has said the factory is no longer "commercially viable". The GMB union said "the fight continues".
Burberry is expected to move production at the Rhondda-based factory to possibly Asia or South America.
Mervyn Burnett, senior organiser for the GMB union, said the firm's decision to delay the closure was a "slight reprieve" but would not stop the campaign to halt the closure.
About 70 Burberry workers and their families protested at the assembly
He said: "The company has now declared that they intend to keep production going until 31st March, which is a slight reprieve only, but the fight goes on to maintain production here on a permanent basis."
The union has organised a series of demonstrations by workers.
This month protests were held outside the designer's store in London and Welsh celebrities have been asked to boycott Burberry products.
The campaign to keep the factory open has been led by Rhondda politicians Chris Bryant MP and Leighton Andrews AM.
In a statement, Mr Andrews said: "We welcome any stay of execution for the factory which is a tribute to the GMB campaign. But the campaign goes on to keep the factory open and the jobs in the Rhondda."
Welsh Enterprise Minister Andrew Davies said it was not a clear three-month extension, but those workers who wanted to continue working could.
He said: "I have pledged my full support to maintain the operation in the Rhondda, as have the unions, and we will continue to make the strongest possible case for these jobs to be retained in Treorchy."
Burberry has previously said the company would look at all options, as the intention to close was "only a proposition".