NZ PM mulling support for Syria intervention without UN mandate: Report

New Zealand Prime Minister John Key said Thursday that he is not ruling out New Zealand involvement in a military intervention in Syria without a mandate from the United Nations.

Key told reporters that he had spoken with UN Secretary General Ban Ki-moon on Thursday morning and was left in no doubt about the gravity of the situation, Radio New Zealand reported.

New Zealand would still prefer the Security Council to negotiate a resolution, but if that did not happen, his country would have to weigh up its options, he reportedly said.

The government had received a general briefing from the United States through its UN diplomats in New York on Wednesday night, but there were no specific requests for action from New Zealand, he said.

New Zealand's response could well end up being moral support for a military response, rather than active participation.

"If it was UN-mandated, that's an easier question to answer I think. New Zealand's historical support has been clear there. If it wasn't UN-mandated then we would need to look at it on its merits at the time," he said.

Foreign affairs spokesperson for the main opposition Labour Party, Phil Goff, called on Key to publish the briefings New Zealand had received and to debate any response.

"John Key has an obligation to be upfront with New Zealanders," Goff said in a statement.

New Zealand should be "outspoken" in seeking UN Security Council agreement to stop all countries providing the arms and financial support that fed the conflict, and should support the work of the UN weapons inspectors, he said.

On Wednesday, Foreign Affairs Minister Murray McCully urged the UN Security Council to agree a course of action in response to the reported use of chemical weapons in the civil war in Syria.

"The New Zealand government remains committed to the Security Council as the appropriate vehicle to address this crisis. It has a clear legal basis for taking action and a clear responsibility to show leadership," McCully said.