A woman who accused US rapper Nelly of sexual assault has asked police to stop their investigation, her lawyer has said.

Nelly was arrested last week after a woman said he raped her on his tour bus in a town outside Seattle, a claim he denied.

Lawyer Karen Koehler posted a letter on her website saying the woman “is telling Auburn Police Department and the King County Prosecutor's Office to put a halt on the investigation of Cornell Iral Haynes Jr”, the real name of the rapper.

It goes on to say she will not testify in criminal proceedings against him, saying the woman “wishes she had not called 911 because she believes the system is going to fail her” and she “wants this to end”.

Nelly's lawyer Scott Rosenblum said news of the letter was “welcome”.

He added: “Her reckless accusation, once investigated thoroughly, was exposed for what it was - a fabrication. A fabrication that has caused Nelly and his family to suffer emotionally and financially.”

He added: “I am suggesting that Nelly seeks a public apology. I am further suggesting that Nelly considers whatever legal options are available to him. Nelly thanks his fans for their unwavering loyalty.”

Nelly - who was on tour after releasing his seventh studio album M.O. - is due to play 15 shows around the UK in November.

The 42-year-old's latest performance was at the White River Amphitheatre in Auburn, Washington state, on October 6.

Following the accusations, the Dilemma singer took to Twitter to deny the “false and defaming allegation”.

In a string of tweets the father-of-two also apologised to his family for “putting myself in a situation where I could be victimised”.