"And the America's Cup and APEC are yet more matters to throw into that mix."
Few of the major projects identified as priorities by the Government and council are expected to be finished by 2021. The council's top priority, the City Rail Link, is not set for completion until 2023.
Bridges said it was "too early to be definitive" about whether the rail link or other projects could be sped up.
But he said there were a few possible "quick wins". While light rail or a bus corridor to the airport cannot be completed within four years, Bridges said there was a possibility that sections of the route could be rapidly upgraded before 2021.
"I'm talking about whether we find the best parts of the network, for example around Hillsborough Rd, where there might be early works that might make a difference to congestion.
"Just how and whether we'd be able to do things sufficiently in time for the America's Cup is very difficult to say. In fact, I suspect it would be hard to.
"Just the legal and land issues take us out to 2019. And that doesn't leave us much time."
The host for the 36th America's Cup has not been finalised, but Team New Zealand has said it wants to host it in New Zealand.
Auckland Mayor Phil Goff's office said the America's Cup and the APEC political conference falling in the same year would be "an exciting time for Auckland".
It also presented many opportunities for the city, a spokeswoman said.
"The Mayor has had some preliminary discussions with central Government on the needs of the city and will continue to have these discussions. The current priority for Auckland is fixing our infrastructure deficit."
APEC, or Asia-Pacific Economic Cooperation, will be the largest event the Government has ever held in New Zealand. The gathering of the world's most powerful politicians will bring between 18,000 and 22,000 people to the city over several months.
The event usually requires traffic diversion and changes to airline schedules to accommodate comings and goings by leaders and ministers from 21 countries.
The America's Cup also attracts tens of thousands of visitors. Analysis of the 2003 event in Auckland showed that the city's economy swelled by $450m, much of which came from superyachts which contributed around $5m each to the economy.
Prime Minister Bill English said yesterday it was probably not realistic for the regatta to be held in any other city than Auckland.
"It may be part of early discussions ... to work out when the peak APEC activity is, because APEC goes on all year, there's something like 23 meetings of all [21] ministers. So of course you wouldn't want to be putting more pressure on Auckland in 2021 than is necessary."
The Government yesterday pledged $5m to Team NZ to help it retain key team members. In a veiled threat, English said further funding was unlikely unless the next regatta was held in New Zealand.