Avaya is a US producer of telecoms equipment
US Telecoms firm Avaya has confirmed that it is considering closing its plant in Monkstown, County Antrim, which it bought from Nortel last month.
Avaya, owned by private equity firms Silver Lake and TPG Capital, bought Nortel's enterprise division out of administration for $915m in December.
About 40% of staff at Monkstown work for the Avaya part of the business.
Trades union Unite is seeking a meeting with management and has said that 140 jobs are under threat.
"Avaya has entered a consultation process following the strategic business decision to potentially close the Monkstown (Northern Ireland) office," a company spokesperson told the BBC news website.
Enterprise Minister Arlene Foster said Invest NI was continuing to build relationships with Avaya.
"I understand that local employees have been verbally briefed about Avaya's intention to consolidate as part of a European restructuring plan," she said.
"At this stage, it is not clear what exactly this means for Northern Ireland but Invest NI continues to build relationships with Avaya, including working very closely with local management, to position Northern Ireland as strongly as possible.
"It would be inappropriate to speculate further until Avaya makes a formal announcement."
Earlier this month Avaya outlined what it called a "roadmap" for integrating Nortel into its existing business. The company said there were overlaps in some areas and that some Nortel products would be discontinued.
On Thursday, it was announced that the Hughes Christensen drill bit factory in east Belfast was to close with the loss of 210 jobs.
Parent company Baker Hughes said its operations would move to Texas.
The factory at Castlereagh has been in operation for 55 years making drill bits for the oil and gas industry.
The company made 135 people redundant last year, blaming a decline in the world market for drill bits.