Delays on construction to widen the Panama Canal could set back the entire project for months, the waterway's administrator warned on Wednesday. Work on the massive canal expansion project has been held up for the past week because of cost overruns. A date to finish the massive expansion project had been set for June of next year, but the past several days' delay could push the completion date back to December, administrator Jorge Quijano told lawmakers at Panama's national assembly. "Two or three months of reduced production and some halted activities... could lead to us finishing the work in December 2015," Quijano told lawmakers. Construction on expanding the canal was suspended last week by the GUPC consortium made up of construction companies Sacyr of Spain, Italy's Salini-Impreglio, Belgium's Jan de Nul and Constructora Urbana of Panama. The dispute that caused the work to be held up is over $1.6 billion in cost overruns in the project, the main part of which is to equip the canal with a third set of locks. GUPC wants Panama to add the sum to the initial contract fee of $3.2 billion The century-old Panama Canal, seen as a marvel of engineering, handles five percent of global seaborne trade. GUPC claims unforeseen geological difficulties have forced them to spend much more on cement than expected. They say that they based their estimates on data provided by the Canal Authority that were incorrect. The canal expansion is one of the world's most ambitious civil engineering projects. The original canal, built by the United States mostly with workers brought in from the Caribbean, was opened in 1914. Quijano earlier Wednesday told reporters that the government had reached partial agreement with the construction companies, which takes them part of the way to resolving the dispute. But he warned that the Panama Canal Authority would not negotiate forever, and could not rule out resuming the mega-project on its own in a week if a deal can not be reached. Modest progress in their talks, "does not mean we have given up on the other alternative, which is to take charge of the project ourselves," Quijano said. He gave no details of what points the two sides had agreed on and what the remaining sticking points were. "Our patience has limits, and we really feel this has to end in a week at the most," Quijano said.