A method and system delivers a cryogenically stored fuel in a gaseous state into the air intake system of a gaseous fuelled internal combustion engine. The method involves measuring the pressure in the vapor space of the cryogenic storage vessel, comparing the measured pressure to a required fuel supply pressure 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 pressure measured in the vapor space of the cryogenic storage vessel is equal to or higher than the required fuel supply pressure. The method further involves activating a cryogenic pump to deliver fuel to the internal combustion engine from the liquid space of the cryogenic storage vessel when the measured pressure in the vapor space is lower than the required fuel supply pressure.