The Department of Infrastructure says it needs more time to complete work on a stretch of the TT course.
Work on surface drains between Glen Helen and Sarah's Cottage has been taking place since last week, and the road has been shut.
The DOI the work is taking longer than first expected despite extended hours from its staff.
As a result, the route will not open this week and the road closure is expected to remain in place until Tuesday, April 2.
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