Kamil Gziut, 29, of Arnhem Way, Donington, pleaded guilty to causing the woman actual bodily harm with intent to commit a sexual offence during a hearing at Lincoln Crown Court.
Gziut, who appeared in court by video-link from prison, had faced a more serious charge of attempting to rape the woman in Albion Street, Spalding, on Saturday November 27.
The Crown Prosecution Service maintain Gziut intended to rape his victim and were given a month to decide if they require a trial on the issue in front of a judge.
Nick Bleaney, defending Gziut, said: “This is a serious sexual assault and that is accepted by the defendant.”
But Mr Bleaney told the court Gziut did not accept that it was his intention to rape the woman.
“He says he has never had sex in his life and was trying to encourage her back to his home,” Mr Bleaney added.
The court heard Gziut had a history of mental health problems and Mr Bleaney asked for a psychiatric report to be prepared on him before he is sentenced.
Judge Simon Hirst adjourned the case until February 18 for the prosecution to decide if they require a trial of issue and remanded Gziut back into custody for the preparation of a psychiatric report.
The Judge told Gziut whatever happened he had pleaded guilty to a very serious offence.
Judge Hirst said: “It is dragging a lone woman into an alleyway, into bushes, and putting his hand around her neck, with the intention of carrying out a sexual assault, even if that fell short of an intention to rape.”
Lincolnshire Police launched an appeal after three men were reported to have come to the rescue of the woman.
Police said a passing motorist was also thought to have helped.