"The advice we've had is that by taking the extra 250-odd each year we are starting to stretch the system a bit but as we've seen this is a fast moving situation.
"As I pointed out in my speech, this is the worse refugee crisis the world has seen since World War II, so we'll just give ourselves some room there."
He said it was not something the Government was looking at immediately and had not thought about numbers, "I'm simply not boxing myself in the corner that we could never move again".
New Zealand has allocated 750 places for Syrian refugees over three years - 600 of which are on top of the annual quota of 750.
He said allowing for refugees above quota was rare.
"I think we are playing our part - we are a small country and doing everything from trying to combat Isil and training people in Iraq right through to financial support programmes [in refugee camps]".
"I'm quite proud of our record. We play our part."
Mr Key said the global response to Syria had prompted action from countries and he was hopeful the same pressure would result in action from the Security Council.
"Millions of people are affected and the Security Council could act, it could ultimately pass a resolution around a no-fly zone or it could pass a resolution around military force as ultimately happened in Afghanistan.
"Those things are possible but they are not possible if the veto is applied and inaction is allowed to prevail."
Mr Key had criticised the power and behaviour of the five permanent members, saying they brokered agreements behind closed doors without involving other members on the Security Council and if one disagreed with an action it would be abandoned to prevent the use of a veto.
Mr Key said that did not mean that New Zealand and the other nine elected members were only a rubber stamp or that the campaign to secure the seat was a waste of time.
He believed New Zealand was contributing.
"We have a job to do the best we can when we're on the Council but equally we have a responsibility to point out its failings.
"No country, no matter how large they are, can ultimately withstand enough pressure if an overwhelmingly large majority put pressure on them.
"If they are really the handbrake in ensuring the world doesn't get the solutions they need, eventually that moral persuasion will have some impact."
He said two of the permanent members, the United Kingdom and France, already supported limits on the use of a veto in cases of mass atrocities.
"I can't guarantee [the others] will change, but we have a responsibility to keep making the point."
