John Key is preparing to attend the Copenhagen summit, with tickets provisionally booked and an announcement set to be made this week.

"We have taken the precautionary step of making some provisional bookings," he said yesterday.

The Prime Minister originally said he would not go but would leave it all up to climate change ministers Tim Groser and Nick Smith.

He then left himself a little wriggle room, saying there was only a 5 per cent chance he would make it.

Mr Key has come under pressure to attend after a flurry of diplomatic activity in the past three weeks which has given greater confidence that a new deal could be sealed there.

President Nicolas Sarkozy of France, conference chairman and Danish PM Lars Rasmussen, and UN Secretary-General Ban Ki-moon made personal pleas for leaders to go when they spoke at the Commonwealth summit in Trinidad and Tobago.

More than 90 leaders are now going to the two-week talks to negotiate a replacement for the Kyoto Protocol. They start on Monday.

Mr Key said he had advice from the Ministry of Foreign Affairs and Trade that the situation had "slightly changed".

Australian Prime Minister Kevin Rudd is understood to have lobbied him to go. But Mr Rudd's own leadership position in the climate change conference has been dealt a blow with the ousting of Liberal leader Malcolm Turnbull over his pledge to support Mr Rudd's emissions trading scheme.

National, with the Maori Party's support, passed amendments to Labour's ETS just a few weeks ago.

Mr Key said the result in Australia was "not entirely unexpected".

"But what it does show is how contentious climate change legislation is and how it is not just New Zealand but every country struggling to deliver on the political goodwill when it comes to climate change."