Acting oil minister Anas al-Saleh said on Wednesday that talks were proceeding between the government and unions to avert the strike, due to start on Sunday over plans to cut some of the workers' benefits and wages.
Sheikh Talal al-Khaled al-Sabah, spokesman for Kuwait's oil sector, said the Ministry of Social Welfare had invited the parties to meet on Thursday to try to resolve the dispute. Kuwait Petroleum Corporation (KPC) would attend the talks.
"There are no negotiations between the unions and the government over the strike," Farhan al-Ajmi, head of the Petrochemicals Industries Company workers union, told Reuters. He said the door for negotiations had been closed since the last meeting with Saleh earlier this week.
"The strike will not be cancelled or suspended until all the demands are met," he said.
The union did not say how long the walkout would last.
Sheikh Talal said that under Kuwaiti laws, no strike can take place while negotiations are under way, urging workers and KPC and its subsidiaries not to "heed calls to obstruct work".
A spokesman for Kuwait National Petroleum Company (KNPC) had said production and exports would not be affected by the strike, and a strategy was in place to deal with this kind of action where extra staff will be used to run operations.
Workers fear reduced salaries, benefits and layoffs will be part of a planned government overhaul of the payroll system in the public sector.
Strikes are fairly common among public sector workers in Kuwait - one of the world's richest countries per capita - unlike in other Gulf states like the United Arab Emirates, where unions are banned.
The other firms where workers plan to join the strike are Kuwait Oil Company, Kuwait Oil Tanker company, Equate Petrochemical Industries Company and Kuwait Gulf Oil Company.
OPEC-member Kuwait pumps 3 million barrels of crude per day and has three refineries with a combined capacity of 930,000 bpd.