The loan for the Autopista al Mar 2 project represents 25% of the total financing required, while China Development Bank will cooperate with another 37%.
A 10-day nationwide strike in May caused disruption to essential services and reduced highway traffic.
Legal uncertainty also damages the participation of other stakeholders in the infrastructure sector, such as insurers.
The mayor ruled out the possibility of taking legal action if the environmental evaluation service approves the controversial project.
Four tenders, for which bids had already been opened, are being halted until the incoming presidential administration decides whether development of the current project will continue.
Converting the San Martín service into an electric-powered line is part of the US$14bn RER program to overhaul Buenos Aires' rail network.
Companhia Energética do Piauí (Cepisa) will be the first of six distributors privatized during an auction on Thursday. Another five subsidiaries will be offered to bidders on August 30.
Just one company presented an offer for a port terminal concession, according to a newspaper.