US Secretary of State Hillary Clinton has postponed her visit to New Zealand following the devastating earthquake in Haiti.

Foreign Minister Murray McCully said Mrs Clinton had rung him to convey the news and had promised to reschedule the visit "as soon as possible".

"Mrs Clinton told me that given the unimaginable scale of tragedy, and the fact that there are no operating institutions left in Haiti, the importance of US leadership in the relief efforts required her to return home immediately," he said.

"The decision to postpone the visit is entirely understandable, given the massive damage and loss of life in Haiti, and the fact that there are a very large number of Americans based there."

Asked if any date had been pencilled in, Mr McCully said there had not but said it would be "at the earliest possible date".

"Obviously their system has got their mind on Haiti and how best they can help," Mr McCully said.

He said Mrs Clinton's plane was in the air, heading to Papua New Guinea when she turned around and headed home.

Mr McCully said it would have been timely to pick up on the whaling issue with the United States, given the upcoming International Whaling Committee meetings later this month but talks were continuing.

Shortly after making the statement on Mrs Clinton's visit, Mr McCully announced New Zealand was making a $1 million contribution to relief efforts in Haiti.

"As the enormity of this disaster emerges, the international community is rapidly mobilising to assist the people of Haiti," Mr McCully said.

He said the $1m was a "starter".

"Saving lives and assisting survivors are obviously the immediate priorities. New Zealand's contribution will therefore be channelled through international relief agencies, such as the International Red Cross and various United Nations agencies, who are already in Haiti and have the ability to respond effectively to a such a disaster.

"As fuller assessments of the damage and the type of assistance required emerge, New Zealand may look at further contributions."

Mr McCully said a New Zealand diplomat had been sent but it was doubtful that the diplomat would be able to get into Haiti, given the destruction.

"You actually do feel a sense of powerlessness when you know that there's someone in extreme distress with people affected by a tragedy such as this," Mr McCully said.

"Not only do we have no capacity on the ground ourselves but others that do have that capacity on the ground have been flattened and talking to Hillary Clinton this morning, she made it clear that just about every institution in Haiti - including the United Nations and others who play a significant role there - have just about been rendered unable to function."

Mrs Clinton had been due to land in New Zealand early on Friday and leave for Australia on Sunday.