He actually switched Iraq's oil sales to euros in November 2000. After the US invasion they switched back to selling oil in dollars again.
The Invasion of Iraq: Dollar vs Euro
Re-denominating Iraqi oil in U. S. dollars, instead of the euro
by Sohan Sharma, Sue Tracy, & Surinder KumarZ magazine, February 2004
SNIP
If OPEC oil could be sold in other currencies, e.g. the euro, then U.S. economic dominance-dollar imperialism or hegemony-would be seriously challenged. More and more oil importing countries would acquire the euro as their "reserve," its value would increase, and a larger amount of trade would be transacted and denominated in euros. In such circumstances, the value of the dollar would most likely go down, some speculate between 20-40 percent.
In November 2000, Iraq began selling its oil in euros. Iraq's oil for food account at the UN was also in euros and Iraq later converted its $10 billion reserve fund at the UN to euros. Several other oil producing countries have also agreed to sell oil in euros-Iran, Libya, Venezuela, Russia, Indonesia, and Malaysia (soon to join this group). In July 2003, China announced that it would switch part of its dollar reserves into the world's emerging "reserve currency" (the euro).
On January 1, 1999, when 11 European countries formed a monetary union around this currency, Britain and Norway, the major oil producers, were absent. As the U.S. economy began to slow down during mid-2000, Western stock markets began to yield lower dividends. Investors from Gulf Cooperation Council nations lost over $800 million in the stock plunge. As investors sold U.S. assets and reinvested in Europe, which seemed to be better shielded from a recession, the euro began to gain ground against the dollar .
SNIP
The unprovoked "shock and awe" attack on Iraq was to serve several economic purposes: (1) Safeguard the U.S. economy by re-denominating Iraqi oil in U.S. dollars, instead of the euro, to try to lock the world back into dollar oil trading so the U.S. would remain the dominant world power-militarily and economically. (2) Send a clear message to other oil producers as to what will happen to them if they abandon the dollar matrix. (3) Place the second largest oil reserve under direct U.S. control. (4) Create a subject state where the U.S. can maintain a huge force to dominate the Middle East and its oil. (5) Create a severe setback to the European Union and its euro, the only trading block and currency strong enough to attack U.S. dominance of the world through trade. (6) Free its forces (ultimately) so that it can begin operations against those countries that are trying to disengage themselves from U.S. dollar imperialism-such as Venezuela, where the U.S. has supported the attempted overthrow of a democratic government by a junta more friendly to U. S. business/oil interests.
The U.S. also wants to create a new oil cartel in the Middle East and Africa to replace OPEC. To this end the U.S. has been pressuring Nigeria to withdraw from OPEC and its strict production quotas by dangling the prospects of generous U.S. aid. Instead the U.S. seeks to promote a "U.S.-Nigeria Alignment," which would place Nigeria as the primary oil exporter to the U.S. Another move by the U.S. is to promote oil production in other African countries-Algeria, Libya, Egypt, and Angola, from where the U.S. imports a significant amount of oil-so that the oil control of OPEC is loosened, if not broken. Furthermore, the U.S. is pressuring non-OPEC producers to flood the oil market and retain denomination in dollars in an effort to weaken OPEC's market control and challenge the leadership of any country switching oil denomination from the dollar to the euro.
To break up OPEC and control the world's oil supply, it is also helpful to control Middle East and central Asiatic oil producing countries through which oil pipelines traverse. The first attack and occupation was of Afghanistan, October 2001, in itself a gas producing country, but primarily a country through which Central Asia and the Caspian Sea oil and gas will be shipped (piped) to energy-starved Pakistan and India. Afghanistan also provided an alternative to previously existing Russian pipelines. Simultaneously, the U.S. acquired military bases-19 of them-in the Central Asian countries of Uzbekistan, Tajikistan, Kyrgyzstan, and Turkmenistan in the Caspian Basin, all of which are potential oil producers. After the invasion and occupation of Afghanistan and Iraq, the U.S. controlled the natural resources of these two countries and, once again, Iraq's oil began to be traded in U.S. dollars. The UN's oil for food production program was scrapped and the U.S. Iaunched its Iraqi Assistance Fund in U.S. dollars. In December 2003, the U.S. (Pentagon) announced that it had barred French, German, and Russian oil and other companies from bidding on Iraq's reconstruction.
http://www.thirdworldtraveler.com/Iraq/Iraq_dollar_vs_euro.html A synopsis of the book "Petrodollar Warfare Oil, Iraq and the Future of the Dollar" by William Clark:
The invasion of Iraq may well be remembered as the first oil currency war. Far from being a response to 9-11 terrorism or Iraq's alleged weapons of mass destruction, Petrodollar Warfare argues that the invasion was precipitated by two converging phenomena: the imminent peak in global oil production, and the ascendance of the euro currency.
Energy analysts agree that world oil supplies are about to peak, after which there will be a steady decline in supplies of oil. Iraq, possessing the world's second largest oil reserves, was therefore already a target of U.S. geostrategic interests. Together with the fact that Iraq had switched its oil export currency to euros -- rather than U.S. dollars -- the Bush administration's unreported aim was to prevent further OPEC momentum in favor of the euro as an alternative oil transaction currency standard.
Meticulously researched, Petrodollar Warfare examines U.S. dollar hegemony and the unsustainable macroeconomics of 'petrodollar recycling,' pointing out that the issues underlying the Iraq war also apply to geopolitical tensions between the U.S. and other countries including the European Union (E.U.), Iran, Venezuela, and Russia. The author warns that without changing course, the American Experiment will end the way all empires end with military over-extension and subsequent economic decline. He recommends the multilateral pursuit of both energy and monetary reforms within a United Nations framework to create a more balanced global energy and monetary system thereby reducing the possibility of future oil-depletion and oil currency-related warfare.
http://www.petrodollarwarfare.com/