Auckland Mayor Len Brown wants SkyCity to take more action against gambling-related harm before a deal is signed off to let it have more poker machines.

The government is close to sealing a deal with SkyCity to build a $NZ350 million ($A274.93 million) convention centre in Auckland.

In exchange, the government is expected to change gambling laws to allow the casino to have 500 more poker machines.

Brown supports the new convention centre but has concerns that SkyCity is not doing enough to address gambling problems.

"If there is a deal ... on the table, then this has to be a crucial part of it," he told One News.

Brown wants the casino to introduce several new measures, including prepaid cards to limit gamblers' expenditure, "cashless" wins, harm-minimisation messages on poker screens and harm-minimisation officers in the casino around the clock.

"Sometimes if the problem is clear and a person is addicted, they cannot deal with their problem, then you've got to get specific personalised help in beside them," Brown says.

In a statement, SkyCity said it was confident its existing harm-minimisation measures are world-class and includes some of the measures suggested by Brown.