Officers say they are doing all they can to locate the man responsible for the "horrendous attack" at around 2pm on Saturday in Openshaw.
After the girl became separated from friends a man approached and led her to an area of wasteland off Kincraig Close, where he sexually assaulted her and then attempted to rape her.
She managed to flee and ran towards a dog walker who raised the alarm.
Once police had arrived they searched the area but could not find the offender.
A man matching the offender's description was seen arriving at Clayton Hall tram stop at 1.33pm, after travelling there on the Ashton line from Edge Lane.
He was also spotted in other locations in Openshaw that day, both before and after the incident took place, police said.
Officers are keeping an open mind as to whether he arrived from another part of Manchester.
"We are continuing to do all we can to find the man responsible for this horrendous attack on an innocent young girl but we still need the public's help," said detective chief inspector Rebecca Boyce.
"We have released images of a man that we wish to speak to in connection with this incident and I would like to appeal to anyone who may recognise him to please come forward.
"If you see the man pictured then please do not approach him but contact us straightaway instead."
Anyone with information should call 0161 856 1146, or Crimestoppers, anonymously, on 0800 555 111.