The CGT (General Confederation of Labour) trade union called all ports to strike over government plans to reform state-run ports.
Inchcape warns that loading and discharging could be stopped during the period and berthing/unberthing postponed.
Two earlier industrial action occurred on August 2 and July 27.
The prolonged 17-day strike on March 14, 2007 at the oil terminals of Fos and Lavera blocked incoming crude tankers and forced chemical firm Ineos to shutdown its Lavera refinery and reduce output.