Jacinda Ardern is expected to lead a global call against fossil fuels during this week's UN Climate Change summit in New York.

She's been invited to deliver the keynote address at the summit tomorrow.

It's tipped to include details of a new trade initiative to remove fossil fuel subsidies and scrap tariffs on climate change technology.

Former government advisor Terrence Looms told Mike Hosking it would be a major policy shift.

"Under the previous government there was a big push to try and attract oil and gas investment."

Ardern will also meet Donald Trump and Boris Johnson during her trip.