The New Zealand dollar held its gains of last week against the greenback before public statements by Federal Reserve chair Janet Yellen amid speculation she may clarify the central bank's view on the start of any interest rate hikes in the US.

House prices around the country have hit a new high with the median price now topping $440,000 but sales are down 10% on last year. (+infographic)

The Kiwi dollar extended its decline against its trans-Tasman counterpart after figures showed Australian unemployment unexpectedly fell last month.

Business confidence remains at multi-decade highs for the first three months of the year, although the strong upswing of previous quarters has flattened out

The kiwi was the worst performing currency tracked by Reuters overnight, falling as low 85.45 US cents after rising as high as 87 cents earlier this week.

Australian business groups are urging the Reserve Bank to exercise caution before considering raising interest rates, given improving signs in the economy are not yet widespread.

The New Zealand dollar is overvalued by between 5 and 15 per cent, the International Monetary Fund reckons.