An HIV-positive man in New Zealand has admitted injecting his blood into his sleeping wife and infecting her with the virus which can cause AIDS.

It is believed the man wanted to give her the disease so she would start having sex with him again.

The man pricked his wife twice with a sewing needle laced with his infected blood, and how she once caught him handling a syringe full of his blood.

The man, 35, admitted infecting his wife, 33, and faces up to 14 years imprisonment.

The man discovered he was HIV-positive, but his wife and children were not, during health checks imposed on them when the family arrived in New Zealand in 2004.

The woman said she wanted to maintain the relationship for the sake of the children but refused to have sex with her husband as she feared she would contract the disease.

She described how in May last year she discovered a sting-like mark on her left thigh and two days later she awoke to a stinging feeling in her leg.

During a routine check-up four months later she found she was HIV-positive and confronted her husband who admitted dipping a needle in his blood and pricking her with it.

"All he said (was) he was sorry. He said: 'I used needles on you because I wanted you to be the same as me so that you can live with me and you won't leave me'," she said.