The United States Navy has expressed interest in using the controversial $850 million Darwin ship lift, the Northern Territory's infrastructure minister says.Construction of the ship lift is scheduled to be completed in March 2027, with workers set to start night shifts to meet the time frame.NT Infrastructure Minister Bill Yan said the NT government has had discussions with US officials."The US Naval attaché was here quite some time ago, I spoke with him about the ship lift and its capabilities," he said."I believe the US are watching this project closely to see how it can benefit them."I know that the US Navy is looking at what we're doing here to see if it will suit their needs."Bill Yan says the NT government has been in discussions with the US Navy. (ABC News: Pete Garnish)More than 100 metres long and 26 metres wide, the ship lift will be capable of lifting large vessels up to 5,500 tonnes for on-land maintenance.The project was first flagged by the NT government in 2015, when it announced a $100 million grant for private industry to get the project started.In the ensuing years the ship lift turned into a fully-publicly funded project, with its cost blowout branded one of the biggest in Australia's infrastructure history.The ship lift is being built on Darwin Harbour. (ABC News: Pete Garnish)The latest increase, worth $30 million, was noted in the NT budget last month, taking the total cost to $850 million — half of which Mr Yan said had already been spent.Despite its massive outlay, the government will receive no direct revenue in return due to contracts signed by former Labor chief ministers.Instead, Australia's largest pearling company Paspaley will operate the facility for profit.Workers are beginning night shifts to finish the ship lift by March 2027. (ABC News: Pete Garnish)Marine complex to complement ship liftLast year a parliamentary committee recommended the Country Liberal Party (CLP) government proceed with the ship lift, saying it would cost almost $600 million to break contracts and ditch it.At the beginning of this year, the government subsequently announced the ship lift would form part of a wider 246-hectare Northern Marine Complex.Mr Yan said the complex would complement the ship lift and be a base for vessel maintenance services."The ship lift in itself is one piece of a larger picture," Mr Yan said."If we're lifting a vessel out of the water, there are all these industries needed to work and repair that vessel — there's electricians, there's plumbing, certainly mechanical, paint, blast and stripping."Anything you put into salt water around here is going to need work done on a regular basis and that's what we're positioning the ship lift and the marine precinct to be able to do."The project was first announced in 2015. (ABC News: Pete Garnish)Asked whether public money would be pumped into creating the marine complex, Mr Yan said the government was paying for ground and infrastructure works."We're already doing work for plumbing, sewerage and power to support this area — we'll do some of that heavy lifting to prepare the marine precinct for investment," he said."But then we want to see private sector investment come in and partner with government and partner with the project."There's interest from across the board, from the private sector, from defence and, of course, I know that our Indo-Pacific neighbours are really looking at what we're going to be able to do here."The ship lift will form part of the Northern Marine Complex. (ABC News: Pete Garnish)ADF a 'close partner' on projectThe NT government has repeatedly spoken about the ship lift's importance to the Australian Defence Force (ADF).The ADF did not directly answer whether they had made a commitment to use the ship lift, but Mr Yan said the ADF had been "a close partner" on the project.Bill Yan says defence is a key partner for the ship lift. (ABC News: Pete Garnish)"The Northern Marine Complex will deliver significant sovereign maritime sustainment capability in Northern Australia, and the Government will continue engaging with Defence to ensure it supports Australia's long-term maritime sustainment and national security needs," he said."I know defence have been winding down their operations over at Larrakeyah [Naval Base] as far as maintenance goes, waiting on [the ship lift] to come out of the ground," he said."The previous [NT Labor] government delayed on the project, which should have been out of the ground years ago … and of course, that has affected defence, but defence are a key partner for us."Although the NT government will not receive any direct revenue from the ship lift, Mr Yan said Territory taxpayers would eventually get some return on their investment."We'll see the returns for the Territory in that business and growth around the [Northern Marine Complex]," he said."As businesses start and employ people, that's where we start to see that larger piece of growth throughout the Territory."We'll pick up some money in payroll tax … we'll hopefully see more people coming to live here."That means more housing, more families and growth of Darwin."The US Navy has been contacted for comment.The NT government says although the ship lift won't generate direct revenue, the wider complex it will exist in will see returns for the NT. (ABC News: Pete Garnish)