The two leaders who had a contentious telephone call last year have been collaborating on strategies to press North Korea over its nuclear weapons program and other issues during Asian leaders' summits in Vietnam and the Philippines.

But the planned dinner was changed to a short private meeting because they had met earlier in the day, officials said.

A spokesman for Mr Turnbull said the prime minister spent half an hour with Mr Trump in the president's waterfront hotel suite.

The spokesman said he didn't know of any other leader who had been invited into Mr Trumps' private quarters. No officials were present.

Publicly, while in Manila, Mr Turnbull has been railing against the North Korea crisis.

"The reckless and dangerous conduct of the North Korean regime has been the main topic of discussion," Mr Turnbull told reporters after he and Mr Trump pulled Japan's Prime Minister Shinzo Abe into a meeting to discuss the threat.

"My job is keeping Australia safe," Mr Turnbull said.

Leaders of the Association of Southeast Asian Nations (ASEAN) will express "grave concern" over North Korea's development of "weapons of mass destruction, including nuclear weapons, and ballistic missile technologies" after lobbying led by Mr Turnbull and Mr Trump.

But Mr Turnbull has been pressing for more than words, telling reporters the key way to bring North Korea's dictator Kim Jong-un "to his senses, without conflict, is economic pressure and that requires concerted action."

"We've got to make sure we keep the squeeze on North Korea," he said.

Both Mr Turnbull and Mr Trump have steered well clear of Asia's two humanitarian crises during the series of meetings, keeping the focus on North Korea, terrorism and trade.

During separate meetings with Philippine president Rodrigo Duterte, who is hosting the meetings, neither criticised the Philippines' so-called "war on drugs" that has left more than 14,000 mostly poor Filipinos dead.

"Look, I had a very good discussion with President Duterte," Mr Turnbull said when asked by a reporter whether he raised the killings.

"We talked about the war on drugs and he's talked about how the leadership of that campaign has been taken over by the drug enforcement agency and he certainly recognises the issues have been raised."

Mr Trump began a meeting with Mr Duterte saying he had "a great relationship" with his Philippine counterpart.

Harry Roque, Mr Duterte's spokesman, told reporters "there was no mention of human rights. There was no mention of extralegal killings" during the meeting.

But human rights and civil society groups want Mr Duterte put on trial at the International Criminal Court for Crimes against humanity over the killings.

Observers saw the opportunity for Mr Trump to press Mr Duterte on human rights as a test of US power, both in the Philippines and the region.

All leaders attending the ASEAN summit in Manila meetings have remained silent on Myanmar security forces' escalation of a brutal offensive against Rohingya Muslims in the country's Rakhine State that has sparked the exodus of more than 600,000 people, the greatest movement of a civilian population in Asia since the 1970s.

In closed-door meetings Myanmar's de factor leader Aung San Suu Kyi told leaders her government is implementing the recommendations of a commission led by former UN Secretary-General Kofi Annan, which includes giving basic rights back to long-persecuted Rohingya.

But the government has refused to condemn documented atrocities by its security forces, blocked UN human rights investigators going to Rakhine and has yet to facilitate the safe return of more than 800,000 Rohingya now living in squalid refugee camps in Bangladesh that international aid agencies say is an unfolding humanitarian emergency.

Mr Turnbull has made no public mention of the Rohingya crisis during his five-day Asian trip.

Mr Trump has not made any comment on the Myanmar atrocities since the security forces escalated a brutal crackdown in Rakhine two months ago.

The UN has described the atrocities as ethnic cleansing and human rights groups say they amount to crimes against humanity under international law.

Asian leaders meeting in Manila plan to sign an accord aimed at protecting migrant workers across the region.

They are also expected to announce some progress towards a "code of conduct" for the flashpoint waters of the South China, where China has been aggressively building-up its military presence.

China, which claims almost all of the waters, opposes any legally bind code and wants the issue to be kept off the agenda of ASEAN meetings.

Asian leaders have been discussing a code of conduct on the South China Sea for more than 15 years, always putting out a statement on progress at the end of their annual talk-fests.