About six weeks ago, he had announced the designation of Boko Haram as in international terrorist group under the Terrorism Suppression Act.
That was one way New Zealand supported international efforts and the Nigerian Government to combat the terrorist organisation, he said.
"The safety of Nigerian citizens is primarily the responsibility of the Nigerian Government, though we're pleased to see members of the international community offering assistance in this case.
"We have not been asked to do so and realistically other countries are better placed to help than us. However we can add our voice to those of Governments and citizens around the world calling for the girls' safe return to their desperate families.
"The education of girls and the respect for rights of women are hallmarks of a developed and successful country. We will continue to follow this situation closely.''
If the Nigerian Government asked for an offer of support, it would be considered because of the seriousness of the situation. But Mr Key thought an approach would be extremely unlikely.
"We are unlikely to be in that position to do anything other than offer the support we have, which was essentially designate Boko Haram as a terrorist group that New Zealand recognises, and offer our moral support.''
Mr Key said the SAS could "theoretically'' be deployed.
"But I don't think it's likely they'd ask. They probably have a range of capability to draw on which is much closer to home.''
Labour's human rights spokeswoman Maryan Street and women's affairs spokeswoman Carol Beaumont last week wrote to Foreign Minister Murray McCully urging the Government to take any steps possible to support the effort by the United States and Britain to recover the girls.
"New Zealand's distance from Nigeria and our size should not prevent us from offering logistical, financial, operational or loud moral support to the international efforts being taking in this urgent case.''
