Workers at the Port of Darwin will keep their jobs when their enterprise agreement ends in 2018, Northern Territory Chief Minister Adam Giles has said after announcing a 99-year lease of the port yesterday.

Chinese company Landbridge, which won the bid to operate the port under a deal worth $506 million, said yesterday there would be no forced redundancies during the term of the current enterprise agreement terminating in June 2018.

Director Mike Hughes would not rule out loss of casual employees or voluntary redundancies.

"We have committed to $35 million [investment expenditure]," he said.

"We have got projects that we are going to be talking to [Port of Darwin CEO] Terry [O'Connor] and kicking off straight away.

"I seriously would be surprised if the answer isn't we will be increasing employment at the port, not decreasing it.

"This is all about growing."

This morning, Mr Giles told 105.7 ABC Darwin he could also guarantee permanent workers would keep their jobs to 2018.

Asked if any workers would lose their jobs after 2018, Mr Giles answered in the negative.

The lease deal has been strongly condemned by the NT Maritime Union of Australia (MUA), which has threatened action and wants assurances workers conditions were protected for 99 years and that jobs would not be contracted out.

"On behalf of the MUA, I strongly condemn the sale of the publicly owned Port of Darwin to a private Chinese investment firm," NT MUA branch secretary Thomas Mayor said in a statement.

Mr Giles told 105.7 ABC Darwin he had spoken with Mr Mayor yesterday and was "in a very brief text message discussion today, following up a few other things."