The leader of Unite, Len McCluskey, has denied a climbdown over the Grangemouth plant dispute calling the union's decision to return to talks "pragmatism at its best".
He told Sky News the plant was "too important" to close and that he is "optimistic that the olive branch that has been offered to [plant owners] Ineos will be taken up".
Mr McCluskey also accused Ineos of presenting workers with a "list of demands" that they had "very little time to consider".
Grangemouth owners Ineos are in last ditch talks with the workers' union, but the workforce is just one of the problems facing the plant.
Thousands of jobs are under threat after a dispute over conditions led to a shock decision to close the petrochemical site in Grangemouth.