Fears are mounting for four New Zealanders who have not been heard from since Hurricane Katrina hit the United States nine days ago.

The Ministry of Foreign Affairs said yesterday that it was worried about not only Aucklander Brendan Clifford-Walsh but also three other people who had not contacted their families since the disaster.

"There's a level of concern there for them," said ministry spokeswoman Emma Reilly.

She said the three were believed to have been in the area affected by the hurricane but not necessarily in the worst-hit city of New Orleans.

It was not known if they were tourists or New Zealanders living in the United States.

Their details have been passed to authorities in America with those of Mr Clifford-Walsh, whose family endured another day yesterday without word from him.

The last contact the 65-year-old made with them was in an email from New Orleans on August 28.

He told his nephew, Chris Walsh, that he had been ordered to evacuate his hotel and go to the Superdome, 20 blocks away.

Chris Walsh said the family were increasingly worried.

"It's now definitely at the point where there's something not right."

Mr Clifford-Walsh's daughter, Melanie McCahill, said she was concerned her father might be injured and need medical attention.

"Each day is becoming more difficult," said Mrs McCahill, wife of former All Black Bernie McCahill.

The Government yesterday pledged $2 million towards the hurricane relief effort through the Red Cross and is sending an emergency management expert to the United States to help with the relief effort.

John Titmus, of the Ministry of Civil Defence and Emergency Management, will leave tonight for a disaster response base in Denton, Texas.

The 57-year-old will head a four-person United Nations Disaster Assessment and Co-ordination team likely to co-ordinate international relief coming into the area.

"I'm looking forward to it but it's going to be difficult, because there are a lot of people there that need a lot of help," he said.

Mr Titmus has 20 years' experience in emergency management, including helping to co-ordinate the response in Sri Lanka to the Boxing Day tsunami.

Prime Minister Helen Clark announced while on the campaign trail in Dunedin that the donation to the relief effort would be provided through the Red Cross on behalf of all New Zealanders.

"The scale of the disaster is greater than we thought a couple of days ago," she said.

"There are still thousands missing and the death toll is rising. There are over 100,000 evacuees sheltering in Red Cross shelters.

"Our hearts go out to those Americans who have lost loved ones and had their homes destroyed.

"We are extending the hand of friendship to the US over the hurricane because obviously emergency systems are strained to the limit and beyond endurance," Helen Clark said.

The US Embassy in Wellington said it deeply appreciated the $2 million donation and gratefully acknowledged the offer of disaster management personnel.

"We're working with the New Zealand Government and with those on the ground in the United States to establish the most effective way to make use of those staff," said acting ambassador David Burnett.

The Prime Minister also had a dig at the National Party, saying a Government that was cutting taxes could not afford to invest sufficiently in infrastructure to respond to natural disasters.

"If you are a tax-cutting small government then you can't meet people's needs," Helen Clark said.

"We have to have a good level of public investment for our whole security as a nation."

She said an urgent Government review was under way into New Zealand's preparedness for a disaster such as Hurricane Katrina.

"We have to think the unthinkable. We are seeing the unthinkable in disasters offshore, whether it is the tsunamis or the terrible hurricanes."