SAVANNAH - A dredging company awarded a $134.5 million contract nearly three months ago won't start deepening the shipping channel to the Port of Savannah until December, Army Corps of Engineers officials said Thursday during a visit by the agency's top general.

The $706 million project to deepen the Savannah River between the port and the Atlantic Ocean to make room for bigger cargo ships has been in the works since 1999. Georgia officials have been eager for dredging to start since Gov. Nathan Deal signed a final cost-sharing agreement with the Army Corps last year.

In early March, the agency hired Illinois-based Great Lakes Dredge and Dock Company to handle deepening the 18-mile outer harbor starting off Tybee Island and extending into the ocean. That's roughly half the length of the overall project.

Lt. Gen. Thomas Bostick, the agency's commanding general, toured the port Thursday and spoke with reporters. After being asked when dredging might start, Bostick consulted his local project leaders and said the soonest would be December. That's because the contractor plans to use large hopper dredges, which the Corps has agreed to keep out of the river channel until late fall to avoid harming sea turtles during their nesting season. The outer harbor will only be open to dredging from December through March.

"The environmental windows have a lot to do with when we can dredge," Bostick said. "That's the primary delay in when we can start."

Seaports across the East Coast are scrambling for deeper water to make room for supersized cargo ships expected to begin arriving via an expanded Panama Canal next year. Some giant ships are already arriving in Savannah, the nation's fourth-busiest container port, via the Suez Canal - but they can only navigate the river channel at higher tides.

Bostick said the Savannah project, which will deepen 39 miles of the river from 42 feet to 47 feet, is moving as efficiently as possible given regulatory and funding hurdles. But he also sounded impatient.

"I would say everything is behind schedule in my mind," the general said, though he added: "It's on schedule given the funding and the time frame we're on now."

The Army Corps declared the official start of construction on the harbor deepening in January when divers began work to raise remains of the Confederate warship CSS Georgia that sunk in the river near the end of the Civil War. Most of the agency's funding for the project this year comes from $266 million the state of Georgia has set aside for its 40-percent share of the project.

The Corps was also able to put $21 million into the Savannah harbor this year and President Barack Obama's administration has asked for $21 million more in the fiscal 2016 budget. But most of the state's money will be used up this year, and the federal government will need to drastically increase funding levels to avoid further delays, said Curtis Foltz, executive director of the Georgia Ports Authority.

"We will need about $100 million in fiscal year 2017 to keep the project on its current schedule," Foltz said.