The New Zealand powered to a new post-float high against the greenback as gains in stocks helped lift global risk appetite, boosting higher-yielding currencies.

Stocks in the United States rallied as progress on a US budget-reduction deal and strong earnings gave investors reasons to be optimistic about the economy’s health, while the euro and European shares rose ahead of an EU summit later this week.

Some investors are hopeful that the EU summit could pave the way for a deal to solve Greece’s debt problems.

The NZ dollar rose from US84.63c at 5pm to a peak around US85.70c early on Wednesday, and at 8am (0600 AEST) was buying US85.57c.

ANZ bank said the NZ dollar exploded through topside levels overnight and never contemplated reversing despite a weaker result in Fonterra’s online auction.

Prices at the GlobalDairyTrade event fell, with the weighted average price for all products down 5.1 per cent, and the weighted average price for whole milk down around four per cent from the previous event.

“The NZD continues the move into the stratosphere. While oxygen levels are almost non-existent at this height there appears nothing that can really dent the move as other alternatives look less attractive,” ANZ said.

The NZ dollar rose against the euro from 0.5995 at 5pm to peak near 0.6060 shortly before 8am. It also spent some time early on Wednesday above A80c against the Australian dollar, the first time above that level in nearly a year. By 8am the kiwi was down to A79.81c.

The NZ dollar also rose to 67.81 yen at 8am from 66.91 at 5pm, with the trade weighted index lifting from 73.24 to 73.90.