The Aussie traded above US91¢ yesterday for the first time since in December 15, after strong demand during the London and New York trading sessions.

Companies that sell raw materials and energy resources made the biggest gains on sharemarkets. In late trading the dollar hit US91.35¢.

A Royal Bank of Scotland foreign exchange strategist, Greg Gibbs, said the Australian dollar's strength against the euro was a return to a five-year average.

''The Australian dollar has gone back to pre-crisis levels and a little to the strong side,'' he said. ''It makes sense that [the Aussie] goes to the strong side because we have had a massive rise in terms of trade and the euro has not.''

Mr Gibbs said the euro was falling against the Australian dollar and other currencies, pulled down by potential problems within the eurozone. ''There are risks around the euro which the market probably has not been paying attention to until recently,'' he added.

''[There is] pressure on the core countries, like Germany and France, to step in and support the other weaker states in the economy.''

Greece and Spain recently had their credit ratings downgraded, and there are problems with eastern European countries which funded their economic expansion by borrowing billions of dollars.