Panama Canal Authority administrator Alberto Aleman said Thursday that the IDB's approval of the loan demonstrates confidence in the project "despite the world financial crisis."
The US$5.25 billion project to construct two wider locks is expected to double the 50-mile (80-kilometer) canal's capacity. They are scheduled for completion by 2014.
The Panama Canal Authority is borrowing up to US$2.3 billion between 2009 and 2011 to help finance the project. It expects to pay that back by increasing ship tolls an average of 3.5 percent a year.
The waterway now moves about 5 percent of the world's cargo.