Mr Turnbull was in New York City on Thursday to address an Anzac Day function organised by the Australian consulate.

The former prime minister praised the first 15 days of Mr Morrison's campaign with the election set for May 18.

"He's doing a great job," Mr Turnbull told reporters of Mr Morrison, who replaced him as prime minister in August.

"It's a close election and I wish him all the best."

The election campaign resumes on Friday after Labor leader Bill Shorten and Mr Morrison agreed to a truce on Anzac Day, with no ads run or political statements made by the leaders.

Pre-poll voting begins on Monday and Mr Turnbull predicted a close election despite Mr Shorten being considered the front runner.

Should Labor be victorious, he will be Australia's seventh prime minister in 10 years.

"I think all Australian elections are close and this one will be close," Mr Turnbull said.

"It's quite complex around the country. But I'm not here to make election commentary and I wish Scott all the best."

Mr Turnbull, who has a residence in New York, delivered the keynote address at a veterans lunch organised by the Australian consulate.

He spoke of the importance of cyber security in policing terrorism and referred to the 253 people killed in the Sri Lanka bombings as well as the 50 slain in terror shootings at Christchurch mosques in March.

"It's more than a century since Australians and Americans first went into battle together in Hamel in France and since then, in every major conflict, we fought together side by side," he said in a speech.

"The battlefields of 2019 are far more complex than they were a century ago; cyber warfare is much different. It offers opponents the ability to inflict damage at relatively low cost to themselves with a high degree of deniability.

"The technology that has done so much good has also given the individual actor or a small group a lethality and a reach which, in years past, was only available to nations ... as we have seen recently so tragically in NZ and Sri Lanka."

AP