Royal Dutch/Shell Group plans to grow its natural gas business relative to its oil assets and intends to supply gas to the United States, the Wall Street Journal reported on Tuesday.

Demand for gas may overtake demand for oil in the next two decades, Sir Philip Watts, Chairman of the Anglo-Dutch company's committee of managing directors told the Journal.

Watts listed the United States and the Asia-Pacific region, including India and China, as places where demand will rise.

"We've taken the view that the relative growth of gas to oil leads to the clear possibility that gas will overtake oil," Watts told the newspaper. Watts also told the newspaper that he expects an increasing need for the United States to import gas.

"The reality is that gradually the basins are getting more and more mature, the return on effort (diminishes), and inexorably, just as more and more oil is being imported into the US, more and more will need to be imported," he said, according to the newspaper's report.

Shell is the world's No 2 publicly traded oil company.

Watts told the newspaper that while the company may take advantage of a good opportunity to acquire gas-producing assets in the United States, the company intends for now to focus on importing into the country.

A Shell spokesman told the Journal that sales of natural gas were about 41 per cent of its total hydrocarbon output last year.