Deploying New Zealand troops to Iraq was decided long ago, and pretending no decision has been made "just isn't honest", Labour says.

Defence Minister Gerry Brownlee yesterday confirmed the defence force had been told it could undertake "special contingency training" for a deployment that could be announced as early as the end of the month.

The contingency training did not mean a deployment to Iraq was imminent, and did not pre-empt a Cabinet decision, Brownlee said.

But Labour defence spokesman Phil Goff said troops had been training for some time.

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Brownlee was questioned on troops training in December, after NZ First defence spokesman Ron Mark had reportedly been told by army sources a group earmarked for deployment had been told to prepare to leave between the end of February and the start of March.

A Defence Force spokesman said in December no instruction had been received from the Government to prepare to go to Iraq, but the Defence Force had "made its own determination to prepare troops for a possible deployment to the Middle East".

Goff said Brownlee's claim that the contingency training did not pre-empt any Cabinet decision was not credible.

"The Government decided to send troops to Iraq long ago," he said.

"The pretence that no government decision has been made just isn't honest."

The reason Prime Minister John Key gave for taking action in Iraq - that he would not sit back while human rights atrocities were committed - was not honest, either.

"This isn't about the need to protect human rights and fight evil," Goff said.

"It's about, as he admitted earlier, the price of 'being in the club' led by other countries such as Australia, the United Kingdom and the United States."

Goff questioned if there was an achievable objective in deploying New Zealand troops to Iraq that justified putting them in harm's way.

"New Zealand cannot do for the Iraqi army what [Iraq] cannot and will not do for itself," he said.

More than $25 billion had been invested by the United States over the past 10 years in training and equipping the Iraqi army, which had made "practically no difference," Goff said.

"Our efforts can do very little to help with the real problems of persistent corruption, deep sectarian divisions and poor leadership which lie behind the incompetence of the Iraqi army," he said.

Humanitarian help to the millions of refugees in the region would be more effective, Goff said.

Cabinet is expected to make a decision about sending troops to Iraq by the end of the month.

Brownlee said New Zealand would wait for a formal request for assistance from the Iraqi Government.