Defence Minister Gerry Brownlee said Monday's Cabinet is likely to discuss the US air strike on Syria two days ago but he's had no contact with counterparts over the weekend.

In his assessment, it was probably a one-off strike and so he was not expecting any request from the United States for New Zealand to contribute anything more than it already is against Isis in Iraq.

"It would be fair to say we are keeping a close watch on it - the whole world is keeping a close watch on it.

"But it looks like it's much more along the lines of a one-off shot-over-the-bows of both the Syrian regime and their supporters to say this sort of behaviour is not acceptable."

He said it was likely to be discussed at Cabinet.

New Zealand was notified in advance of the strike as a matter of courtesy because it was part of the US-led Coalition against Isis in Iraq.

"That still remains the main target. I guess [the US] want to make sure that anyone involved with them in various military activities understands what they are doing."

Asked what would happen if it escalated and New Zealand was asked to contribute more than verbal support, Brownlee said the Prime Minister would receive such a request through the Ministry of Foreign Affairs and convene a process to consider it.

"But it is not likely in my view. We are already, per head of population, well and truly doing our bit in Iraq at the moment."

New Zealand and Australia are running a training mission in Camp Taji for Iraqi forces fighting Isis in Iraq, with New Zealand contributing 106 Defence Force personnel to the effort.

Australia which, unlike New Zealand, is a formal ally of the United States, has also been involved in air strikes with the US against Isis in both Iraq and Syria and an advise and assist role near the front line.

For several weeks the US has been involved in marshalling forces around the Syrian city of Raqqa, an Isis stronghold, in preparation for an expected assault.

- NZ Herald