The Belgium international claimed on Tuesday that he would ply his trade in Manchester next season, without revealing whether he would be joining City or United.
However, the 21-year-old has now hinted that Chelsea's Champions League triumph on Saturday is making him reconsider his options.
"It is possible that Chelsea's arrival at the negotiation table will delay things, as nothing is done until I sign a contract," he told Canal + after Lille's 4-1 victory against Nancy on Sunday, during which he scored a hat-trick.
"Chelsea can make you hesitate, next year they will play in the Champions League. So we will see."
Earlier in the week, Manchester City midfielder Samir Nasri said that his side had the edge over their cross-town rivals in the race for Hazard, who is rated by Lille at €40 million.
The creative midfielder, who was on Monday named Ligue 1's player of the season for the second year in a row, scored 21 goals in all competitions in 2011-12.