Former Alberta premier Peter Lougheed warns that the United States will soon want more of Canada's water – and politicians should be preparing to fend them off.

Lougheed called for an all-party declaration in the House of Commons that would affirm Canada's refusal to allow bulk exports of its fresh water supply.

"We should not export our fresh water; we need it and we should conserve it," Lougheed said in a speech to the Calgary branch of the Canadian Club on Wednesday.

"We should communicate to the United States very quickly how firm we are about it."

Lougheed, Alberta's premier from 1971 to 1985, said he can see water becoming more valuable than oil.

He said studies have found that almost half the U.S. states are going to be short of water in less than 10 years, predicting Washington would come looking for Canadian water in three to five years.

"It's not included in the free trade agreement now, and so we should take a very firm position," he said.

"And if we take the firm position and communicate that, then the Americans are less likely to come forward and argue that the water transfer is part of the free trade agreement."

Lougheed said he supported a deal signed a day earlier by political leaders from Ontario, Quebec and eight U.S. states, which is aimed at banning large-scale water diversion projects from the Great Lakes.

The agreement, signed at the Great Lakes Governors Leadership Summit in Milwaukee on Tuesday, was primarily aimed at blocking parched southern states from siphoning off huge amounts of Great Lakes water.