The International Labour Organisation says Fiji unions believe implementing the interim government's latest decree would be the nail in their coffin.
The Essential National Industries Decree was gazetted last month but is still to come into effect.
The executive director of the ILO, Guy Ryder, led a delegation to Fiji last week, and met with the interim prime minister, interim attorney general and other key stakeholders.
Mr Ryder says his organisation relayed to the interim government its fears for the safety and security of trade union activists, and also concerns over the decree.
"We have to see now what the right way forward will be, we have to see if the government will display, perhaps a greater willingness in the future to take on board the issues we've tried to raise very clearly with them."
Guy Ryder says the ILO hopes dialogue with Fiji's interim government will remain open following their visit.
Fiji's interim attorney general, Aiyaz Sayed-Khaiyum, says the decree is not aimed at getting rid of unions.