A method and system is disclosed for delivering a cryogenically stored fuel in a gaseous state into the air intake system of a gaseous fuelled internal combustion engine. The method comprises determining the flow rate capacity in the engine system's fuel delivery line, comparing the determined flow rate capacity to a required flow rate demand and supplying fuel in gaseous state directly from the vapor space of the cryogenic storage vessel to the fuel delivery line that supplies fuel to the engine, when the flow rate capacity is equal to or higher than the required flow rate demand. The method further comprises activating a cryogenic pump to deliver fuel to the internal combustion engine from the liquid space of the cryogenic storage vessel when the determined flow rate capacity is lower than the required flow rate demand.