Boris Johnson has praised plans for Northern Powerhouse Rail (NPR) as "very, very exciting" but maintained the costs of the HS2 project need to be looked at.
The Tory leadership front-runner made the comments as he visited theconstruction site at Manchester Airport's new Terminal 2 extension, which isexpected to open next year.
Bosses at the airport have made it clear to Government they want both Northern Powerhouse Rail (NPR) and HS2 to happen and provide a "global gateway" for the north with quicker and more frequent rail journeys to the airport.
On Tuesday, Mr Johnson was enthusiastic about the case for NPR as Transport for the North chief executive Barry White and Manchester Airport group chief executive Charlie Cornish outlined its benefits.
He later told reporters:
This is going to be the heart of Northern Powerhouse Rail and they are making a very, very good case here for £39 billion investment in east-west connections from Liverpool to Manchester, Bradford, Leeds.
Mr Johnson appeared more cautious on the merits of HS2 and said there was "a legitimate question to ask about how the money is being spent".
Just in my own constituency in Uxbridge they suddenly discovered that they did not have a sufficiently long extension lead for the tunnel boring machines.
Asked whether his stance had anything to do with HS2 running through hisconstituency, he said:
The awful truth is HS2 certainly doesn't do my constituency any particular favours but I have resolutely refused to say I would cancel HS2 because, as I say, I hesitate before doing things that would stop great public infrastructure projects.
Mr Johnson asked for a review of the HS2 scheme by its former chairman Douglas Oakervee, which is due to be completed by December.
The extended departure terminal at Manchester Airport will more than double in size as part of the airport's £1 billion transformation. The first phase of the programme opened in April with the launch of a newpassenger pier and a 3,800-space multi storey car park.
When the terminal extension is complete and opened the existing Terminal 2 building will close for refurbishment before it will be fully operational by2022.