Marathon last-minute negotiations between the government and union umbrella group UGTT failed to avert Thursday's strike by public sector workers. The stoppage is expected to affect airports, ports, hospitals and other public services.
Demonstrations are planned at the national union headquarters in the capital Tunis and around the country.
The International Monetary Fund has urged public sector salary freezes and other reforms in exchanges for loans to Tunisia's struggling economy.
President Beji Caid Essebsi has called for calm. Thursday's strike comes after new tensions erupted last month when a journalist set himself on fire to protest unfulfilled promises of Tunisia's 2011 Arab Spring revolution.