The atomic-kinetic calculations of gain at 41.8 nm in Pd-like xenon are performed. The interpretation of known experiments has proved that x-ray laser in Pd-like xenon is feasible in the extremely wide range of atomic densities: 10 17 [Xe 8+ ] 3 × 10 19 cm −3 . This result is due to the large cross sections (and rates) of level excitations in Pd-like xenon by electron impact. We propose a highly efficient tabletop x-ray laser pumped by optical-field ionization in a xenon cluster jet. The efficiency of ∼0.5% is possible with a pump laser pulse energy of 0.001 J and an intensity of ∼10 16 W/cm 2 .