Lawmakers on Friday approved a national referendum on whether the government should undertake the biggest modifications to the Panama Canal since it was opened in 1914.

The $5.3 billion project calls for a construction of a third set of locks on the canal that would reduce long lines of ships trying to cross the canal and allow larger ships to pass through.

"It is a historic moment," said Legislature President Elias Castillo. "For the first time, Panamanians will decide about the future of the waterway."

The exact date of the referendum will be announced after the bill is signed by President Martin Torrijos, who has endorsed the project.

The canal, 105 feet above sea level at its highest point, uses a series of parallel locks to lift ships to Lake Gatun for the transoceanic passage.

Countrywatch:Panama

Large container ships now just barely fit through the canal's locks. The new locks would be able to handle those ships.

Opponents of the proposed canal expansion contend the project is risky because it is based on uncertain projections about maritime trade and the world economy.

Union workers and supporters have formed a group called "National Union for No," which claims the project lacks an accompanying social development plan and solid financial resources, and will put the country in debt.

Officials have said they would pay for the upgrades through loans and toll increases for ships using the canal.

Recent polls indicate that a majority of Panamanians favor the expansion.

Panama took over the administration of the waterway on Dec. 31, 1999, when the U.S. military presence in Panama ended. The United States is the main user of the canal, followed by South American countries and China.