The influence of electromagnetic forcing on self-sustained oscillations of a jet issuing from a submerged nozzle into a thin vertical cavity (width W much larger than thickness T) has been studied using particle image velocimetry. A permanent Lorentz force is produced by applying an electrical current across the width of the cavity in conjunction with a magnetic field from three permanent magnets across its thickness. As a working fluid a saline solution is used. The magnetic field is in the north-south-north configuration, such that the Lorentz force can be applied in an up-down-up configuration or in a down-up-down configuration by switching the direction of the electrical current. A critical Stuart number N c was found. For N < N c , the jet oscillates with a constant Strouhal number St, independent of the Reynolds number Re. For N > N c and an oscillation enhancing up-down-up configuration of the Lorentz force, St grows with N as St ?N??? . In contrast, for N > N c and an oscillation suppressing down-up-down configuration of the Lorentz force, all jet oscillations are suppressed.