A process for producing ammonia synthesis gas, where a natural gas feedstock (10) is reformed in a primary steam reformer (12) and in a secondary reformer (14) at a pressure of at least 35 bar; the product syngas (16) at the output of the secondary reformer is cooled and subject to catalytic medium-temperature shift, converting the CO into CO2 and H2; downstream said medium-temperature shift, the carbon dioxide is removed from the syngas by physical absorption.