Wow... that could be the start of a lot of domino's...

The last folks to do this were Iraq: (note that this was less than 2 years before the invasion by the USA).

Iraq: Baghdad Moves To Euro

By Charles Recknagel

Baghdad's switch from the dollar to the euro for oil trading is intended to rebuke Washington's hard-line on sanctions and to encourage Europeans to challenge it. But the political message will cost Iraq millions in lost revenue. RFE/RL correspondent Charles Recknagel looks at what Baghdad will gain and lose, and the impact of the decision to go with the European currency.

Prague, 1 November 2000 (RFE/RL) -- Iraq is going ahead with its plans to stop using the U.S. dollar in its oil business in spite of warnings the move makes no financial sense.

Baghdad this week insisted on and received UN approval to sell oil through the oil-for-food program for euros only after 6 November. Iraq had threatened to suspend all oil exports -- about 5 percent of the world's total -- if the body turned down the request.