A faulty gene that appears to prevent some men from being able to father a child could pave the way for a new form of contraception for men.
Women have had access to oral contraception for over 40 years, but there is no effective equivalent for men.
However, scientists at the University of Iowa have now identified a gene that is involved in some cases of male infertility and that could be used as a target for drugs that aim to reduce fertility.
Co-lead author Dr Michael Hildebrand, a postdoctoral researcher in otolaryngology at the university's Roy J. and Lucille A. Carver College of Medicine, revealed: "We have identified CATSPER1 as a gene that is involved in non-syndromic male infertility in humans, a finding which could lead to future infertility therapies that replace the gene or the protein.
"But, perhaps even more importantly, this finding could have implications for male contraception."
The findings are published in the American Journal of Human Genetics and take scientists a step closer to providing men with a new contraceptive option.
Research conducted by UK scientists at the Medical Research Council indicates that men would be willing to use oral contraception if it was available to them.
At present, the only options available to men are condoms - which have a 98 per cent rate of effectiveness when used correctly - and vasectomy, where the tubes that carry sperm to the penis are cut, sealed or blocked under a local anaesthetic.