Greenspan, addressing the Senate Committee on Energy and Natural Resources, said spiking natural gas prices had already impacted on some gas consumers, especially ammonia producers and petrochemical feedstock operations.

"If North American natural gas markets are to function with the flexibility exhibited by oil, unlimited access to the vast world reserves of gas is required," it was reported by the Bloomberg news service.

There are currently a number of new LNG importing facilities in varying stages of planning and construction on the mainland US.