"It would be unfortunate if members have to resort to strikes again, but we are committed to getting a positive result," the Community and Public Sector Union's Stephen Jones said.
IBM GSA could not immediately be reached for comment.
About half the 3,500 employees at IBM GSA working on a Telstra contract are original Telstra staff and are covered by a different agreement than those who joined IBM GSA at a later date.
IBM has notified the Community and Public Sector Union (CPSU) by letter, after six months of negotiations, that it is unwilling to discuss the issue of putting all the workers under one business agreement.
"They're refusing to talk about an agreement that would cover all workers at IBM GSA working on the Telstra contract," Jones said. "We don't believe there are any grounds why IBM should be treating some employees as first-class and others as second-class citizens."
Staff who aren't covered by the original enterprise agreement don't enjoy the same conditions of employment as other employees, according to the CPSU.
"We believe they're not getting as good a deal," Jones said.
The CPSU is planning a counterattack it says involves national and international action, including linking up with IBM worker organizations around the globe.
"They're taking a keen interest in what is going on in Australia," Jones said. "We aren't put off by the fact that IBM is multinational. With the advent of the Internet and growing disquiet about outsourcing and globalization, companies like IBM can no longer treat their workers or the public with arrogance."
IBM GSA laid off 60 employees last month, sparking a four-day strike by workers before a more worker-friendly agreement was reached.
Staff writer Rachel Lebihan reported from Sydney.