Unions were meeting the company on Thursday after presenting alternative proposals aimed at saving jobs in South Wales.
Sources said Tata rejected the plan and were pressing ahead with proposals for a greener form of steelmaking to cut emissions and stem financial losses.
Unions will consult their members on how to respond to job losses, with industrial action not being ruled out.
Sources said Tata accepted a union plea to keep the hot strip mill open over a transition period, supporting hundreds more jobs.
A Tata Steel spokesperson said ahead of the meeting: “We have recently announced a joint agreement between Tata Steel and UK Government for a proposal to invest in state-of-the art Electric Arc Furnace steelmaking in Port Talbot.
“We are committed to meaningful information sharing and consultation with our trade union partners about the plan to develop sustainable steelmaking in the UK and to find solutions for concerns they may have.
“While those discussions are ongoing it would not be appropriate to comment further.”