Expectations that the US Federal Reserve will announce measures tomorrow to prop up the flagging economic expansion bolstered Wall St overnight.

The New Zealand dollar held above 79 US cents as leaders from the Group of 20 nations increased pressure on European Union policy makers.

Wall St was up overnight as investors opted to rekindle optimism the US Federal Reserve will come up with new stimulus measures.

The New Zealand dollar fell from a one-month high after Federal Reserve Chairmen Ben Bernanke failed to signal further quantitative easing for the US.

The Reserve Bank will not lower the official cash rate below 2.5 per cent in its review next week, says Westpac chief economist Dominick Stephens.

The dollar rose almost one US cent on optimism European policymakers will act to stimulate the region's economy and provide aid for Spanish banks.

The New Zealand dollar fell after G7 leaders nations agreed to a coordinated response to Europe's deteriorating financial crisis, though gave no guidance on how to do so.