The U.S. is launching a diplomatic offensive to meet the growing threat to its energy security from powerful and increasingly wealthy producers who are flexing their new geopolitical muscles.

Faced with oil-related challenges on a number of fronts - from Venezuela to countries of the former Soviet Union - U.S. Secretary of State Condoleezza Rice said yesterday that she will appoint a special envoy for energy issues to deal with countries that use their oil and gas for political means.

Her action underscores the growing concern about security of energy supplies in the United States, and the shrinking pool of reserves available to multinational corporations as producing countries put their resources in the hands of national oil companies.

But the U.S. government's more explicit support for giant oil companies such as Exxon Mobil Corp. could backfire, as producing countries see it as further evidence that the American government is as prone to geopolitical machinations over energy as anyone else.

"It is a really important part of diplomacy," Ms. Rice said. "In fact, I think I would go so far as to say that some of the politics of energy is warping diplomacy in certain parts of the world."

Ms. Rice said the envoy would pay particular attention to Central Asia, where President Vladimir Putin has exerted Russia's traditional influence to frustrate U.S. plans to build pipelines from oil-rich countries such as Kazakhstan.

Senator Richard Lugar, the leading Republican on the Senate foreign relations committee, said Russia is clearly using its ballooning oil wealth as a political weapon. He said he travelled recently to the former Soviet republics of Georgia, Kazakhstan, Azerbaijan, Turkmenistan and Ukraine and urged them to co-operate with the West on energy security.

"Russian foreign policy is now largely based on maximizing the political leverage and financial earnings of its energy supplies and dominating the transport of energy in Eurasia," Mr. Lugar said.

Across the globe, there are mounting challenges for the United States and the Western companies that have traditionally supplied it with oil, including increasing competition from emerging countries like China and India, and the rise of resource nationalism in producing countries like Venezuela and Russia.

State-owned, national oil companies have exclusive access to some 77 per cent of the world's proven conventional oil reserves, forcing multinational like Exxon to focus more on unconventional sources like oil sands, and more expensive, offshore developments.

Canadian consumers are not immune to security of supply issues. While the country is a major exporter of crude oil from Western Canada, Eastern Canadians rely on imported oil to fuel their vehicles and heat their homes. Petro-Canada has had assets nationalized in Venezuela, and has been the victim of resource politics in Russia when state-owned OAO Gazprom decided to jettison a planned liquefied natural gas terminal.

David Kirsch, a market analyst with PFC Energy Group in Washington, said the U.S. diplomatic effort is particularly aimed at oil-rich Kazakhstan. The Central Asian country once appeared friendly to the West but has recently been demonstrating a more nationalistic bent and a closer relationship with Moscow.

But Venezuela's dispute with Exxon Mobil over the country's nationalization of oil company assets has been a major preoccupation in Washington this week, following President Hugo Chavez's threat of an oil embargo.

OIL COMPANIES' ACCESS TO RESERVES

Global proven oil reserves: 1,148 billion barrels

6%: New Russian companies, with limited access to international companies

6%: Full access to international oil companies.

11%: Reserves controlled by National oil companies where international companies have some access.

77%: Reserves controlled by National oil companies, and off limits to international companies (IOCs)