A multi-billion-dollar expansion of Panama's canal to triple its capacity will likely miss yet another completion deadline and now won't be finished until June, according to the waterway's administrator.

"The inauguration will still take place in the second quarter, but more towards June," Jorge Quijano told AFP on Thursday.

A month ago, Panamanian President Juan Carlos Varela had said the work would be completed "around the month of May."

That in itself was another delay after a series of missed deadlines for the expansion of the 80-kilometer (50-mile) canal, which is over a century old.

Work to enlarge the waterway so that it can handle more traffic and bigger cargo ships started in 2007 and was originally supposed to have finished in 2014.

But overruns and contractual disputes pushed that back to April 2016, then to May this year, and now, according to Quijano, by yet another month.

The cost of the project has ballooned from an initially budgeted $5.3 billion to around $7 billion.

Quijano said the latest delay was due to repairs on fissures detected in August in one of the canal's new locks which he said were now complete.

The Spanish-led GUPC consortium handling the expansion on Thursday started filling two reinforced locks with water to test the repairs, a process that will take 35 days.

Around five percent of the world's commercial shipping passes through the Panama Canal.

The Central American country currently earns $1 billion a year in revenue from shipping fees for using the canal. With the expansion, it hopes to triple that within a decade.