Papua New Guinea's long-running political saga has taken another twist with the Pacific nation's parliament voting to delay this month's scheduled national elections for six months.

Thursday's vote looks set to prolong the back-and-forth power struggle between Michael Somare, the former prime minister, and Peter O'Neill, the current prime minister, over who should be the head of government.

The move came despite repeated assurances from O'Neill that polling would go ahead as planned.

According to the Australian Broadcasting Corporation, the reason for the delay was because parliament was told electoral rolls were not ready and police were not ready to provide sufficient security.

Bob Carr, Australia's foreign minister, had previously warned of possible sanctions against Papua New Guinea if the elections were not held as planned.

Australia shares an important trade relationship with Papua New Guinea, a former Australian territory rich in mineral resources including oil, gold and copper, and crops such as coffee and cocoa.

But in a parliamentary speech, Belden Namah, the deputy prime minister, warned against foreign intervention following the decision.

"Whatever Mr Bob Carr says about sanctions, I want to say ... do not threaten the independent state of Papua New Guinea," Namah said. "You must respect our wishes."

In August last year, O'Neill took office with the support of parliament after Somare was ruled ineligible to be a member of parliament due to illness and absence from the parliament.

But the country's supreme court in December ruled Somare be reinstated as a member of parliament, and a military mutiny also tried unsuccessfully to restore him to office.