Proposed changes to the company pension scheme could see workers retiring at 65 instead of 60.
But Tata said it was committed to offering "still very competitive" pension arrangements.
It employs 7,000 people in Port Talbot, Llanwern in Newport, Shotton in Deeside, and Trostre, Carmarthenshire.
Tata also has plants at Scunthorpe, Rotherham, Hartlepool and Redcar.
Steel unions Community, GMB and Ucatt said traditionally, because of the demands of the job, it was not uncommon for workers to take early retirement but under the proposals this would go and they would have to work until they were 65.
The company said the scheme was facing a financial shortfall, mainly due to people living longer.
It has been consulting with about 17,000 workers about replacing it with a "more balanced solution" of a defined contribution scheme.
A spokesman said: "We will consider employees' views before making a final decision. Tata Steel remains open to unconditional talks with the unions to find resolutions to the very substantial challenges facing the pension scheme."
Roy Rickhuss, general secretary of Community, said: "This is not a situation we wanted to find ourselves in. The unions were prepared to discuss changes that resolved the challenges faced by the scheme but Tata rejected that constructive offer."
Dave Hulse, national officer for steel at GMB said: "Our members are determined to stand up for their pensions and they will now have the opportunity to show their resolve by voting for strike action."
Unite is expected to follow suit in sending out ballot papers.
Ballot papers are being posted out to union members at Tata Steel UK over industrial action in a dispute over pensions.