The 1.2km tunnel valued at US$148mn is expected to open to the public by the end of the month.
Investors must have legal certainty about continuity of works, says transport minister Gerardo Ruiz Esparza.
Back in April, ASUR acquired majority stakes in two companies in charge of operating a total of 12 airports in Colombia.
Construction companies and train manufacturing firms have already expressed interest in financing the construction of an express rail line to connect the capital and its future international airport, says a senior government official.
A previous concession contract for the road was terminated in 2014, while an attempt to tender the same road in 2015 failed.
The upgrade investment at two plants will boost production capacity and reduce costs.
A large number of tenders to repair damaged road infrastructure does not have enough bidders to be implemented.