PM Helen Clark may hope that a lengthy campaign could help her win
New Zealand Prime Minister Helen Clark has called a general election for 8 November, aiming to win a fourth term in office.
However, Ms Clark's Labour Party has trailed the opposition National Party in opinion polls for the past year.
Economic woes and a scandal-hit foreign minister have given the opposition its best chance of power in a decade.
But the country's aversion to the Iraq war and strong anti-nuclear stance are unlikely to change, whoever wins.
Ms Clark, 58, a successful campaigner, told a news conference on Friday that the election would be about trust.
"It is about which leader and which major party we New Zealanders trust our families' and country's future with," said the prime minister.
"What I see is that as the election nears people are focusing very much on what the real choice is. And at that point it comes down to what matters most to our families and our communities," she said.
The latest date on which elections could have been set was 15 November, and some analysts have suggested Ms Clark's choice of date will give her time to claw back support.
Correspondents say the nation's economy is expected to be a key issue in election. A recent cut in interest rates may help Labour, and promised tax cuts are due to take effect in October.
Public opinion polls show the Labour Party trailing the main opposition National Party by at least 6.5 percentage points - an improvement on a 16-point gap earlier in the year.
New Zealand's voting system is mixed-member proportional representation, which shares power with smaller parties, in a single-house parliament usually of 120 seats.
Ms Clark's government has led a minority parliament in recent years, relying on parties such as United Future and New Zealand First for support.
New Zealand First leader, Winston Peters, has been her foreign minister but stepped down on 29 August as he is now under investigation for donations allegedly made to his party by wealthy business figures.
Ms Clark has distanced herself from Mr Peters in recent weeks.
Just before the election announcement, Ms Clark's government passed a promised major piece of legislation to set up an emissions trading scheme.
Parliament will be dissolved on 3 October and nomination day is 14 October, allowing for a five-week campaign period.
"I do believe the future of New Zealand is at stake," Ms Clark said.
"I believe that Labour has shown through its record in office that we can be trusted with the future of New Zealand."
She said her Labour Party was "ambitious" for New Zealand, whereas the opposition party was "ambiguous".
National leader John Key did not immediately comment.