Builders are hoping to claim an extra one billion for the second stage of the WestConnex motorway in Sydney.

The motorway which links the inner city out to the western suburbs was estimated to cost $45.3 billion to complete.

According to the Australian, CPB Contractor - formally known as Leightons want the extra one billion for variations on the second stage of the motorway.

The WestConnex motorway which links the inner city out to the western suburbs was estimated to cost $45.3 billion to complete

The claim is believed to be because of a planning approval delay on the WestConnex.

Government sources have revealed they are hoping to negotiate how much the major contractor will be paid.

The company is one of two preferred for the third stage of the WestConnex.

This is the third recent case allowing private companies to claim hundreds of million for mishaps in the government's infrastructure projects.

CPB Contractor - formally known as Leightons want the extra one billion for variations on the second stage of the motorway

Northwest Rapid Transit - a link from the north west to the city, cost the state $400 to $500 million due to cracked concrete spans.

Infrastructure company, Acciona put a bid to claim and extra $1.2 billion to build the Sydney light rail.

In the past fortnight, the Spanish construction company has laid 490m of light rail track in, but the government says the contractor needs to be putting down an estimated 2000m of track a month to meet their deadline.

The next stage of the WestConnex is planned to open in the first half of next year.

It is expected to be the new M4 twin tunnels between Homebush and Haberfield.