Prime Minister John Key indicated a delayed start date of 2020 when he announced government financial backing of the $2.86 billion project.
But he has said the start could be brought forward if Auckland Transport could lift annual train patronage to 20 million passenger trips "well before 2020" and show a 25 per cent leap in CBD jobs. The target is almost double current train patronage.
Mayor Len Brown said it was possible construction could start early.
"The Prime Minister has left open the possibility of an earlier start for the CRL and we will continue to discuss timing with the Government. My view is an earlier start would be significantly more cost effective and allow Auckland to reap the economic benefits sooner, but those are discussions we are yet to have."
Mr Pritchard said the sooner work could start, "the better".
"We are supporters of the City Rail Link, and the ability for public transport to bring more people into the city would be good for our business," he said. "From a business perspective the sooner the better, and if this acts as a catalyst to bring forward the date that would be good."
The shopping centre sits on land required to build and operate the rail link. Two rail lines will emerge from Britomart travelling below QEII Square and Downtown, before curving under Albert St as they head south to connect with the line at Mt Eden.
Mr Brown said the agreement to try to co-ordinate construction was "another great step" in the progress of the CBD rail link. "Today we celebrate 10 years since the first train service at Britomart and here we are a decade later agreeing to negotiate a kick-start for the next exciting phase of our city's rail future," he said.
The link will be able to carry 30,000 people an hour at peak times, with trains running every 5 to 10 minutes.
Train timetable
2020
Govt date to fund half the cost of $2.86 billion City Rail Link, unless Auckland Transport can lift train patronage and CBD jobs.
2016
Auckland Council's preferred start-date and scheduled start for construction of new shopping centre above the link.
- Additional reporting, staff reporter