Manchester United are ready to challenge for PSG striker Kylian Mbappe.Mbappe is inside the final year of his current deal at PSG and a major summer target for Real Madrid.However, ESPN says United are prepared to challenge for the striker.But any move will be dependent on Mbappe staying with PSG this season and running down his existing deal.Real Madrid are prepared to bid for the France international this month to take him off PSG's hands.