Steel giant Corus has been warned it risked provoking "crippling industrial action" unless jobs and key skills at a mothballed plant were retained.
The Teesside Cast Products site at Redcar in north-east England was mothballed last month, threatening 1,600 direct jobs and thousands more in supply firms.
Corus blames the crisis on an international consortium which pulled out of a 10-year contract to buy steel slabs.
Unions offered Corus a 14-day period of grace to take a "different course of action." That deadline ends on Monday when the National Steel Co-ordinating Committee (NTUSCC), which represents all unions in Corus, will hold a meeting.
Union leaders have said a failure to provide a satisfactory solution will provoke an "industrial response".
Any industrial action would exclude the at-risk Teesside workforce, but may include the Teesside Coke ovens and Beam Mill and other Tata Corus sites from around the country.
Community Union general secretary Michael Leahy said: "We have made it very clear that if Corus fail to produce a satisfactory answer to the Teesside question, Community and the other unions will look for an industrial solution.
"The pressure is squarely upon Corus today to find a solution which will retain the key skills and jobs of the workforce and return the Teesside plant to production.
"The Trade Unions require Corus to show good faith at this point as their actions over the past year have threatened to shatter 40 years of partnership between unions and management.
"The pattern of action from Corus through this recession has been to turn away from the helping hand from the unions and to squeeze their loyal and hard-working employees."