Leighton Holding’s shares have dipped after the construction giant announced that the completion date for Brisbane’s Airport Link toll road has been pushed back by almost two months.

The company announced in a statement on Monday that the Airport Link should be open to traffic on or before August 20, instead of the previous forecast of June 30.

Leighton, which owns the Thiess and John Holland companies involved in building the project, said it had made adequate commercial allowances for schedule changes and the delay would not impact on its profit guidance for 2012.

While the major construction works were expected to conclude in June, the mechanical and electrical fitout, plus testing and commissioning, would still need to be completed, Leighton chief executive Hamish Tyrwhitt said.

“The construction elements of the project will be completed in line with our expectations, with final commissioning and safety testing programmed to be completed through July,” he said in the statement.

“More than half of the tunnel is now in the commissioning stage with the testing of services including lights, fans, surveillance, fire deluge and ventilation systems, and tolling systems underway.”

Leighton, Australia’s largest construction company, has experienced financial troubles in recent months after ongoing problems with the Brisbane Airport Link and Victorian water desalination plant projects.

The company has previously blamed wet weather in Brisbane for delays in the toll road’s construction.

In March the company cut its full year profit by nearly a third because progress on the two projects had been worse than expected.

Leighton said the deterioration in the two projects was expected to cost $256 million in pre-tax earnings.

The latest full year profit forecast for Leighton is $400 to $450 million, compared to the $600 to $650 million it estimated in February.

At 1453 shares in Leighton Holdings were 53 cents, or 2.66 per cent, lower at $19.43.