A failing Syrian ceasefire and strained relations between the US and Russia threaten to derail the UN Security Council summit Prime Minister John Key has called to seek a resolution on the crisis.
The meeting is due to take place on Wednesday in New York and was scheduled well before the week-long ceasefire began unravelling.
On Tuesday Syria's military declared the ceasefire was over, Reuters reports.
As Syrian or Russian warplanes bombed rebel-held areas, US and Russian officials began holding closed-door meetings in Geneva in a bid to save the truce.
It was damaged at the weekend when US aircraft mistakenly bombed Syrian soldiers.
More than 60 soldiers were reported killed, and Russia suggested the US military had deliberately undermined the ceasefire.
That was rejected by the US, and its UN ambassador walked out of an emergency Security Council meeting.
Mr Key wants the meeting he will chair to reach a consensus on a way to end the war, but the prospects are bleak after events over the last 48 hours.
Mr Key said on Monday international tensions should be set aside, because they were outweighed by the urgent need to seek a way through what he has called "the most devastating crisis of our time".
But it's being reported from New York that even getting Russia and the US to sit at the same table could be a challenge.