A man in the US allegedly forced his pregnant girlfriend to sign an abuse contract allowing him to beat her whenever he wanted.

Under the contract, Graydon Smith, 31, was allowed to punch, kick and throttle his girlfriend so long as he didn't harm her pregnant belly, the Daily Mail Reports.

The abuse contract was revealed after he was arrested by police for assaulting his girlfriend at their Seattle home.

The victim's stepfather had called police after he witnessed Smith allegedly throttling his daughter.

At the time of the arrest, she was found with cuts and bruises to her face and told police her boyfriend was responsible for the assault.

According to the Daily Mail, the unemployed Smith admitted he had forced his girlfriend to sign the contract giving him licence to carry out the abuse.

Seattle police detective Elizabeth Ellis told the Daily Mail: "Graydon made her sign a statement giving him permission to physically abuse her anywhere on her body except on her pregnant belly."