Wellington  - New Zealand Prime Minister John Key said Monday that he was sending a letter to Afghan President Hamid Karzai protesting a law Karzai signed that decrees a wife is obliged to fulfil the sexual desires of her husband.

But he said at his weekly news conference that the law he earlier described as "abhorrent" would not colour his government's decision on whether to expand New Zealand's military commitment to Afghanistan

because they were different issues.

"We are trying to address the issue of terrorism and making sure that New Zealand is playing its part to reduce the potential risk and threat from terrorism," he said.

"If we were to stop involvement with that because of what we think is an unacceptable law they're passing in relation to sex in marriage, then in our view, we would be putting the world in greater risk, and that's not appropriate," Key said.

The new Afghan law recently passed by parliament is meant to legalize Shiite family law, but critics said it effectively bars women from leaving their homes without the permission of their husbands and it legalizes rape within marriage.

New Zealand has about 130 army engineers working as a provincial reconstruction team (PRT) in Afghanistan, and Key dodged a question about whether New Zealand planned to expand this deployment to include crack Special Air Services forces as US President Barack Obama aims to step up the foreign military presence in Afghanistan.

Foreign Affairs Minister Murray McCully attended the recent international conference on Afghanistan in The Hague and was due to meet US Secretary of State Hillary Clinton in Washington this week.

"I'm not ruling it out, but neither are we ruling it in at this point," Key said when asked about a possible Special Air Services deployment.

"I've made it clear that our commitment to Afghanistan is quite substantial in terms of the PRT," he said.

"Now, that doesn't mean that we couldn't increase our commitment there - every other country is being asked to do that - but whether we would do so is something we have not decided, and that is something the foreign minister will be communicating to Secretary Clinton." (dpa)