Significant damage was caused to the road surface after a vehicle caught fire on Sunday on the exit of the Gooseneck.
The Department of Infrastructure said its paver team will plane out and resurface both lanes before new line markings are applied.
A spokesperson said: ‘The carriageway will be planed out this morning. Unfortunately, the heavy rain forecast on the hills this afternoon has meant that final surfacing can only go ahead tomorrow morning.’
It is planned that the A18 Mountain Road will reopen to two-way traffic at 4.30pm tomorrow (Tuesday 10 June).