CALGARY With oil prices falling and competition growing from other energy producing nations, any move to secure a greater market share will come at a high price for OPEC countries, Sheikh Ahmed Zaki Yamani told world oil executives here Monday.

Some are concerned the 11 nations of the Organization of Petroleum Exporting Countries (OPEC) may enter a phase where they wish to defend their market share rather than targeting their production levels to a world oil price, AFP quoted Sheikh Yamani as saying.

But he warned: OPEC's dash for market share will be doomed to failure unless the organization is prepared to endure sharp falls in its oil revenue."

Sheikh Yamani, who addressed the 2002 Canadian Energy Research Institute World Oil Conference via satellite link from his London office, had been energy minister in Saudi Arabia for 24 years and now is chairman of the Center for Global Energy Studies.

He told 150 senior oil executives here that while OPEC nations hold the trump cards of low production costs and abundant reserves many OPEC nation budgets -- like Saudi Arabia, Kuwait and Venezuela -- rely heavily on oil revenues to fund their social programs.

And as world prices have plummeted from more than $30 to less than $18 a barrel, all oil producing nations are feeling the heat.

OPEC has led a movement to cut production and drive up prices, but major producers outside OPEC, like Russia and Mexico, must deliver on recent promises to cut production by 460,000 barrels a day as well, to have an impact on prices.

"But i doubt whether the non-OPEC producers will deliver their pledged cuts," Yamani said. "OPEC will have to go it alone with its production cuts if it wants to push oil costs up above $20 a barrel," he said.