New Zealand will not be giving official recognition to one side in Venezuelan politics - because the government says it's not its practice to do so.

Photo: AFP

The United States is calling on the international community to pick a side in the dispute over who should be recognised as Venezuela's leader.

President Nicolás Maduro is under pressure after his rival Juan Guaidó declared himself "acting president" on Wednesday.

Several countries, including the US, the UK, Canada and some Latin American nations, already back Mr Guaidó as president.

But Russia, China and Syria are still recognising the socialist leader Nicolás Maduro, who also appears to have the backing of the military.

Discussions at the UN on Saturday were tense as nations clashed on how to resolve the crisis in Venezuela.

US Secretary of State Mike Pompeo accused Russia and China of "propping up a failed regime" and said it was time to "support the Venezuelan people immediately".

"No more delays, no more games. Either you stand with the forces of freedom, or you're in league with Maduro and his mayhem," he said.

New Zealand's Foreign Affairs Minister, Winston Peters, said it's not New Zealand's practice to make statements recognising governments.

Venezuela should be allowed to decide its own fate through free and fair elections, he said.

Mr Peters said New Zealand expressed concern about the elections Venezuela held last year, and those concerns remain.

Why is Maduro being challenged?

He was re-elected to a second term last year - but the elections were controversial, with many opposition candidates barred from running or jailed.

The National Assembly argues that the presidential position is actually vacant because the election was unfair - and that under the constitution this means that Mr Guaidó, as head of the National Assembly, should take over as acting president instead.

Tens of thousands have held protests over Venezuela's economic crisis - including an annual inflation rate that the opposition says reached 1,300,000 percent last year.

Mr Maduro has so far retained the support of the country's military, but Mr Guaidó has asked them to "put themselves on the side of the Venezuelan people" and back him instead.

- RNZ / BBC