Veto likely in Security Council push for tribunal to inquire into MH17 crash

It is a diplomatic showdown - and New Zealand is in the thick of it.

As foreign ministers from across the world jetted into Manhattan for a day of high stakes negotiations over the downing of Malaysian airlines flight MH17, Foreign Minister Murray McCully was preparing to preside over a stormy session of the United Nations Security Council on Thursday morning (NZ Time).

Russia is widely expected to exercise its veto power as one of the council's five permanent members to block the formation of an independent tribunal into the MH17 crash. 

It will be the second time during New Zealand's month-long presidency that the veto has been invoked. Not since the 1970s has the council seen the veto power exercised in such quick succession.

McCully, who will be in the hot seat chairing the debate, spent the 24 hours beforehand in meetings with his Australian, Dutch and Malaysian counterparts as talks were held across Manhattan in a bid to stave off the Russian move.

But with Australia and Russia taking equally hardline but opposing positions, McCully acknowledged late on Tuesday New York time that a veto appeared unavoidable.

"It's fairly certain at this stage," he said.

Russia upped the ante ahead of the vote, claiming the establishment of an international tribunal would be a "dangerous step" leading to a surge of confrontation in global affairs.

Meanwhile, Australian Foreign Minister Julie Bishop vowed she would not let the Russian veto deny justice to families who lost loved ones in the MH17 crash.

The crash killed 298 people including 39 Australians and two New Zealanders - Rob Ayley and Mary Menke. Countries that lost people in the crash are pushing for a tribunal that can prosecute whoever is found responsible once a Dutch Safety board investigation is complete in October.

The plane was shot down last July over rebel-held east Ukraine during heavy fighting between Kiev's armed forces and pro-Russian separatists.

Suspicions have centred on the separatists.

McCully said New Zealand's job as president had been to canvass all the options for an accommodation that might avoid a veto. 

But it also had to respect the views of those nations with grieving families.

He hoped the debate would not be too confrontational.

"We are trying as president to run a session tomorrow which reflects the solemnity of the occasion, which shows the Security Council has regard to the feelings of those whose [family members] were lost in the tragedy."

New Zealand campaigned on Security Council reform in its bid for a temporary seat - and restraint over the use of the veto was a key plank.

The veto power is held by the five permanent members, who also wield huge control over decisions by the organisation, which has 10 temporary members on rotation.

New Zealand has tried to use its seat on the council to spark wider debate on the need for reform, including informal gatherings at its ambassador's residence across the road.

But while there is widespread support for reform among the elected members and wider UN membership, the so-called P5, or permanent membership, is able to block any significant progress.

The permanent members are Russia, China, France, Britain and United States.