The girl had walked through the M621 underpass next to Holbeck Moor Park, in Holbeck Moor Road, between 6.50pm and 7.10pm on Wednesday, March 1, when she was approached by a man who tried to befriend her and offered her a lift.
A male passer-by intervened and the man left the scene in vehicle, believed to be a silver Citroen people carrier.
He was described as a very dark skinned black male, aged in his thirties to forties with an American accent.
Detective Inspector Dave McDougal, of Leeds District CID, said: “We are treating this incident as suspicious and are carrying out extensive enquiries to identify the man involved. We would like to hear from anyone who saw a man fitting the description in the area on foot or in that vehicle or who has any information that could assist the investigation.
“Officers from the local neighbourhood team have been made aware and are increasing their patrols of the area and linking with local schools to offer suitable advice and support.”
Anyone with information is asked to contact Leeds District CID via 101 quoting log number 1416 of March 1 or call the independent charity Crimestoppers anonymously on 0800 555 111.