KANSAS CITY, Kansas (Reuters) - A Kansas man who donated sperm to a lesbian couple so they could have a child said on Wednesday he is shocked the state is now trying to make him pay child support.

William Marotta, 46, donated sperm to Jennifer Schreiner and Angela Bauer under a written agreement that he would not be considered the father of the child nor liable for child support. A daughter, now 3, was born to Schreiner.

But in October, the state of Kansas filed a petition seeking to have Marotta declared the father of the child and financially responsible for her after the couple encountered money difficulties.

Marotta will ask the court in a hearing January 8 to dismiss the claim, which centers on a state law that the sperm must be donated through a licensed physician in order for the father to be free of any later financial obligations. Marotta gave a container of semen to the couple, who found him on Craigslist, instead of donating through a doctor or clinic.

The case is seen as having repercussions for other sperm donors. Sperm banks routinely provide sperm to people who want to conceive a child on the understanding that the donors are not responsible for the children.

Kansas is seeking child support from Marotta, including about $6,000 in medical expenses related to the child's birth, according to its petition.

"This was totally unexpected," Marotta said in a phone interview. "The very first thing that went through my mind was that no good deed goes unpunished."

The case has attracted national attention. Shannon Minter, legal director for the National Center for Lesbian Rights, said Wednesday "it is unfortunate and unfair" that Kansas is seeking money from a sperm donor.

"It certainly might have a negative effect on other men's willingness to help couples who need a donor, which would be harmful to everyone," Minter said.

"I also think it undermines everyone's respect for the law when you see it operate so arbitrarily."

Kansas officials are required under the law to determine the father of a child when someone seeks state benefits, said Angela de Rocha, spokeswoman for the Department for Children and Families. The couple was compelled to provide that information, which led to investigation of the sperm donation.

Marotta should be declared the father and subject to financial claims because he donated the sperm directly to the women and not through a physician, as required by Kansas law, the state's petition states.

Marotta said he's had virtually no contact with the child, but that he and Schreiner have remained cordial. He said she was pressured by the state to provide his name as the sperm donor.

"To me, ethics need to override rules," he said.

Lawyers for Marotta argue that he had no parental rights because of his agreement with the couple and cannot be held financially responsible.

They cite a 2007 case in which the Kansas Supreme Court ruled against a sperm donor seeking parental rights because he did not have any such agreement with the mother, lawyers for Marotta said.

"So now, we are flipping the argument around," Marotta attorney Ben Swinnen said Wednesday.

If the father had no legal parental rights in the 2007 case, Marotta should be declared to have no parental obligations in the current case, Swinnen said.

Marotta, a race car mechanic, responded to an ad on Craigslist from someone offering to pay $50 for sperm donations, but he made the donation for free. Marotta said he and his wife have no children of their own but have fostered a daughter. Marotta said he was simply trying to help a couple wanting a child.