Itau Unibanco Holding SA, Latin America’s biggest bank by market value, is preparing to lend as much as $300 million to companies building a toll road in Colombia, people with direct knowledge of the matter said.

The borrowers are a consortium building the Pacifico 2 highway under Colombia’s 4G infrastructure program, said the people, who asked not to be identified because the negotiations are private. Goldman Sachs Group Inc. participated in a 4G financing in February, when it underwrote a $260.4 million bond for the Pacifico 3 highway.

A government agency provides guarantees in the event tolls fall short of forecasts, allowing banks to book it as if it had Colombia’s sovereign risk and at the same time gain returns of a riskier security, profiting from the difference, two of the people said. The Goldman Sachs deal was rated BBB- by Fitch Ratings, one level below Colombia’s rating.