The former prime minister urged the Morrison government to tread carefully on a decision about state-owned Landbridge's agreement.

"We've got to be very careful to be seen as a trusted, reliable partner," Mr Turnbull told the National Press Club on Wednesday.

"Going back in time and trying to break a lease - and that would not be legally straightforward - it could open up a whole Pandora's box of problems that probably could be best avoided."

The government is weighing up the national security implications of a Chinese company leasing the Port of Darwin.

Earlier in the month, Prime Minister Scott Morrison said he would wait for a Defence review into the arrangement before making a decision.

Mr Turnbull said the advice from Defence, ASIO and other national security agencies while he was prime minister recommended not interfering with the lease.

"There are other assets in Australia, I would have to say, held by Chinese state-owned companies, particularly in the electricity sector, which are arguably more sensitive than the Darwin port lease," he said.

"Undoing deals that have been done is something you want to think very carefully about."

Australia-China relations are at their lowest point in decades after a series of deep rifts over diplomacy, trade and security issues.

Australian Associated Press