Prime Minister John Key says leaked cables from the US Embassy in Wellington which form part of the massive Wikileaks release this week could cause some embarrassment, but does not believe there is anything more serious in the cables than that.

Mr Key said he was briefed "at a very high level" on the broad content of some of the cables.

"There's bound to be one or two that might lead to embarrassment but nothing more serious than that."

He would not reveal what he was briefed on, saying he preferred to wait and see if the cables would be released in their entirety.

Nearly 1500 cables from the US Embassy in Wellington are included in the more than 251,000 cables the Wikileaks website has released to selected media, The Guardian has reported.

The texts of the 1490 cables have not yet been released, but the codes summarising their subject matter show there was a cluster of cables relating to Afghanistan and military operations on the day Prime Minister John Key announced a new SAS deployment to Afghanistan and in the days following.

There were also scattered cables relating to Afghanistan in the months leading up to that announcement. Fiji is another common subject matter in the cables.

Twelve of the cables are marked with the highest possible security classification - 'Top Secret - No Foreigners' - according to magazine Der Spiegel.

There were also 20 marked 'secret' and 53 marked 'confidential - not for foreigners'.

The rest are a mix of confidential and unclassified documents.

Fourteen unclassified documents from the US Auckland consulate will also be released.

There was a further cluster of cables in November 2008 when the National government came into power. Mr Key said the US Embassy had not told him what they had written about him personally in much detail "but I'm sure it will be glowing".

Mr Key would not comment on one cable which revealed the United States had ordered diplomats to collect intelligence on top United Nations' officials - including the position of former Prime Minister Helen Clark who is now the head of the United Nations Development Programme.

The papers show diplomats were asked to gather biometric information as well as details such as credit card numbers.

The Guardian, Der Spiegel and the New York Times are among the media granted copies of the leaked documents.

They have revealed American diplomats were asked to collect detailed personal information on senior United Nations officials in July 2009.

Other revelations in the cables include:

- Saudi Arabia repeatedly asked the US to invade Iran to destroy its budding nuclear programme.

- The US believes China mounted a hacking campaign into computers of Google and Western Governments.

- Worries about 'Islamist tendencies' and incompetent advisers in Turkey's Government have been voiced by US diplomats.

There are 4330 documents marked 'Top Secret - No Foreigners', 11,322 marked 'Secret', 4678 marked 'Confidential - No Foreigners' and 97,070 marked 'Confidential' among those released by Wikileaks.

A further 133,887 are unclassified.