A protest march had also been planned in Nadi on Saturday, but the Fiji Transport Authority refused to issue a permit, saying it would impede the safe movement of traffic.
Several union leaders who were arrested on Wednesday were released from police custody late on Thursday, but the secretary of the Fiji Trades Union Congress, Felix Anthony, and about two dozen of his colleagues were still being held, the congress said. No charges have been laid.
The Fiji Trade Union Congress' offices were also searched by police on Thursday. In a statement, the congress said the raid interrupted an afternoon meeting of the executive board.
The congress's Attar Singh said the crackdown had left the union with no option but to postpone Friday's planned protest.
"But because the police are refusing to allow people to gather at any one place, including private properties, such as union properties, in light of that nobody will be able to assemble in any case, and for that reason, primarily, the protest had to be deferred," Mr Singh said.
Despite the cancellation, Mr Singh said the domestic and international attention had far exceeded expectations.
Meanwhile, the opposition National Federation Party said Fiji had become a police state following the union crackdowns.
Its leader, Biman Prasad, labelled the arrests as persecution, harassment and intimidation, and called for the immediate release of all those who were detained.
In New Zealand, about 30 protesters picketed outside the Fiji High Commission in Wellington. The president of the New Zealand Council of Trade Unions, Richard Wagstaff, said the crackdown was an atrocious response from the Fiji government to people exercising their democratic right to protest.
"Unions around the world are looking at this and we will stand up, and we expect nations in the Pacific including New Zealand to make it clear to the Fijian authorities that we cannot tolerate this in our region," he said.