US sperm donor claims to have fathered over 100 children, sets sights on 2500

A US sperm donor who calls himself a 'miracle maker' and claims to have fathered over 100 children has travelled Down Under to help Australian women avoid becoming "spinsters".

Going by the pseudonym 'Joe Donor', the man told Australia's 60 Minutes on Sunday he's attempted more than 800 inseminations across the US, South America and Australia, which have resulted in more than 100 babies.

He says his goal is to eventually father over 2500.

While a vial of his "super sperm" for  artificial insemination will incur a hefty fee, Joe's preferred method of conception is unprotected sex, which he performs free of charge.

But he's under no illusions the sexual encounters will lead to love.

"I'm basically only having sex to get women pregnant," he told 60 Minutes.

"I'm not chasing rainbows (or) fantasies."

Joe says has few medical checks and no legal contracts to offer the women he inseminates.

"Some people, they want to do a background check, (or a) drug test," he laughs.

"And I'm like, 'you know you're not giving me the keys to the nuclear missiles, we're just making a baby'."

On his Twitter page, Joe promises he "creates sperm donation successes with multiple women", revealing a video of his alleged children all sharing the same "identical laugh".

"What you see is what you get. Contact Joe Donor now to get yours," he writes.

Nine News reports the comments have left lawyers and doctors worried that he's preying on vulnerable women, and leaving their health at risk.

Australian lawyer Stephen Page says he believes Joe Donor is "dangerous".

"I just think he's mad, and dangerous, and these women shouldn't be going anywhere near him," Page says.

Joe hasn't revealed if he'll make the trip across the ditch to offer his services to Kiwi women. But if he doesn't meet his goal of 15 Australian inseminations, anything is possible.