The kiwi dollar has this week hit new 15 month highs against the US dollar as the world waits on a key speech from US Federal Reserve chairperson Janet Yellen.

The New Zealand dollar has traded as high as US73.35c this week, shrugging off six official interest rates cuts over that period.

US dollar weakness continues to be the major driver of the kiwi's strength, NZ Forex's Alex Hill told The Economy Hub today.

Over the past 12 months the market had been let down by the US Federal Reserve which indicated it was ready to raise US rates but so far has not.


With US rates at just 0.5 per cent, New Zealand's record low rates of two per cent still looked good to investors.

"So what we're seeing yield hunters still wanting to get involve with the kiwi," Hill said.

Yellen will deliver a key speech at the central bankers conference in Jackson Hole Wyoming this weekend (Sat morning NZT).

If the speech indicates a strong willingness to start raising US rates then we should kiwi dollar fall.

But there are already concerns in the market that she won't be that strong.

"At the end of that speech, the first question she is going to be asked i: when will you raise rates," Hill said. "We're looking for those magic words becuase they are running out of excuses."

None of the big global events such as China's slowdown or Brexit had stopped market growth and the US job story was starting to look good.

For now the kiwi looked likely to stay strong but it did have a track record of climbing slowly and falling fast.


"When she goes lower, it will happen quickly," Hill said