Union leaders in Guinea say they will not enter talks with the government until emergency powers imposed last Monday are relaxed.
An 18-hour curfew has been imposed to stop further protests
Their refusal came at the same time as West African leaders met Guinea's President Lansana Conte to try to find a solution to the current impasse.
Union leaders want President Conte to relinquish his near-absolute power.
More than 100 people have been killed in clashes with the Guinean security forces during anti-government protests.
One union leader, Rabiatou Serah Diallo, said the meeting with the government had been cancelled for the time being.
"We asked for the lifting of martial law, security for union members, an end to night house searches and the carnage," he told the French news agency AFP.
But the National Assembly President Aboubacar Sompare said the union bosses did not attend the meeting because security documents that would have allowed them to travel despite a curfew had not yet been delivered to them.
Guinea's military reportedly arrested 300 opposition supporters in a series of raids during Friday night and took them to military camps.
The detainees were picked up in the inland towns of Mamou, Dabola, Koundare and Kerouane.
The BBC's Will Ross in the Guinean capital Conakry says that so far President Conte has shown no sign of giving in to the pressure to end what is effectively martial law.
He is having talks with regional envoys led by former Nigeria military leader Ibrahim Babangida, who is seen as a close ally.
Mr Babangida told a news conference that the West African grouping Ecowas would not like to see Guinea "run into a very chaotic situation".
"From the experiences we've got with wars in Liberia, Sierra Leone and Bissau Guinea, I think we should find a solution here," he said.
The Guinean leader has in recent months appeared reluctant to accept outside mediation, our correspondent says.
The US has condemned the imposition of martial law and the civilian deaths.
In a strongly worded statement on Friday, the US embassy in Conakry criticised "the suspension - even partial - of civilian rule, the use of lethal force against the civilian population, the abrogation of basic freedoms, and the roll-back of the democratic process".
France, the former colonial power, has urged Mr Conte to negotiate a political settlement.