John Key's special session chairing the UN Security Council on the Syria crisis overnight tonight has a heightened significance after the bombing of a UN convoy delivering aid near Aleppo on Monday.

It has sparked outrage and suggestions it amounts to a war crime, if deliberate.

Russia or the Syrian Air Force are thought to have carried out the bombing in which, according to Reuters sources, 18 of 30 trucks were hit and at least 12 people killed, even though all parties had been notified about the aid delivery.

It follows an accidental strike by US forces on Syrian troops at the weekend killing at least 60 and putting strains on a week-long truce negotiated between the United Sates and Russia and which led to heated exchanges and walk-outs by ambassadors on the Security Council.

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The two men who negotiated the truce, US Secretary of State John Kerry and Russian Foreign Minister Sergey Lavrov, are expected to attend the Security Council debate.

Now the truce is looking closer to collapse. But Key wants the Security Council to salvage it.

The Prime Minister told reporters in New York yesterday that it made the special session on Syria even more critical.

"I don't have all of those facts but what I do know is the world needs Syria to be in a better place and the Syrian people most certainly need that.

"We can point fingers all day at each other and we can obviously identify the things that have gone wrong but it is a pathway for making things right that is critically important.

"All we can really do at the Security Council is put pressure on everybody to hold hands and see if there is more that we can do."

Asked about Australia's possible involvement in air strikes against Syrian Government troops at the weekend that violated the truce deal, Key said: "My genuine concern is not about which particular plane and which particular country it's associated to. The real concern is that there are these subsequent actions post the negotiated ceasefire.

"The question we all have to ask ourselves is not which country dropped a bomb accidentally or otherwise but what does it take to actually give some respite for I think the people of Syria and that's really what the leaders need to focus [on] now."

New Zealand is sharing the Security Council this month, the second time it has done so in its two-year term on the council.

It chose to run a special session on Syria several weeks ago before recent events.

Key will make a speech to the UN General Assembly about lunchtime Wednesday, New Zealand time.

The Syrian Conflict

1.

The Syrian civil war began as pro-democracy demonstrations against the regime of President Bashar al-Assad.

2. Russia and Iran support the Assad regime while the United States and Saudi Arabia support the anti-Government rebels.

3. Isis controls parts of Syria and is the common enemy of just about everyone.

4. A US-led coalition has conducted air strikes against Isis in Syria; the Syrian Air Force has conducted air strikes against Isis, rebels and civilians and blocked humanitarian aid.

5. The Russian Air Force joined the conflict a year ago to support Syria.

6. The Syrian civil war has claimed more than 250,000 lives in five years.

7. The UN estimates that 18 million people still live in Syria, down from 24.5 million when the war began.

8. An estimated 4.8 million Syrians have fled the country, many to neighbouring Lebanon, Jordan and Turkey.

9. More than 6 million Syrians have been displaced internally.

10. Russian and US foreign ministers Sergey Lavrov and John Kerry negotiated a truce which would see an end to Syrian Air Force strikes against anti-Government rebels, humanitarian aid to besieged areas and joint military action by Russia and the US against Isis and another jihadist group, Jabhat Fateh Al-Sham, formerly the al-Qaeda aligned al-Nusra Front.

Sources: United Nations and BBC.