The England full back had turned down Manchester City and in private has long indicated his desire to join United, with a £27million deal outlined.
However, the lack of an official announcement over the 18-year-old Southampton star’s future prompted a recent Chelsea enquiry.
Southampton have rebuffed offers so far for captain Adam Lallana with Liverpool needing to find and extra £5m to cover payments to Bournemouth.
Dejan Lovren, Morgan Schneiderlin, Jay Rodriguez, Calum Chambers and Victor Wanyama have also been subject to enquiries.
Manchester City, meanwhile, retain an interest in Ashley Cole.
They expect bids for Aleksandar Kolarov and want a centre back and defensive midfielder with Chelsea target Eliaquim Mangala and Mehdi Benatia of Roma at the forefront of their thinking.