The closure will affect the section between Km43+500 and Km54+000 from 5 am until further notice.
The Lam Dong Department of Construction is coordinating with local authorities and contractors to carry out urgent repairs along the route after landslides damaged parts of the mountain pass.
Authorities warned that construction activities had caused rocks, mud and debris to spill onto the roadway, creating slippery and potentially dangerous conditions for motorists.
Alternative routes between Dalat and Phan Thiet include National Highway 20, National Highway 28B, National Highway 55 and the B’Sa-Da P’Loa Road.
The Department of Construction has instructed road maintenance authorities and contractors to install barriers, warning signs and traffic diversion systems during the closure.