The Premier League giants have agreed on an initial fee of €65m with Barcelona but negotiations over the potential add-ons have dragged on.
Barcelona want the €20m add-ons to be easily achievable in order to get the €85m they are keen to have from the Dutchman’s departure.
Manchester United are also negotiating personal terms with the 25-year-old who is open to the move to Old Trafford this summer.
But it has been claimed that Manchester United’s initial plan to have De Jong on the flight to Thailand on Friday is unlikely to happen.
Negotiations are ongoing but Manchester United are still some way away from finalising an agreement.
They are not expecting to complete the deal in time for the Dutchman to be in that flight to Thailand for their pre-season tour.
Tyrell Malacia and Christian Eriksen are expected to be confirmed as Manchester United players in time for the pre-season tour.
And the Premier League giants are also pushing to complete a deal to sign Ajax defender Lisandro Martinez this week.