The mayors of the Wellington region have unanimously backed funding for the $300 million expansion of the Wellington airport's runway.

The region's nine councils will have to contribute around $150 million towards the cost - 60 percent of that coming from Wellington City.

Forum chair and Upper Hutt City mayor Wayne Guppy says the rest can be funded from an average rate increase of 1.3 percent across the region.

"We believe it's one of the major movers economically for Wellington and the middle part of the country.

"If you look at the business case, it's very compelling. OK not only for the Wellington economy but certainly for the middle part of the country."