But one analyst, John Blaxland of the Australian National University, said such persuasion will be difficult and the "opportunity might already have passed" because Pakistan has grown closer to China in recent years and feels less obliged to listen to Washington than it did immediately post-September 11.

Mr Trump is set to deliver a major address late morning Australian time that will almost certainly involve an increase in US troop numbers and broader authority for military leaders. Australia has already committed an additional 30 military advisers, taking its total to about 300. Forty-one Australian soldiers have been killed in Afghanistan since 2001, and 261 injured.

Afghanistan is becoming more violent, with the Taliban retaking territory and other groups such as the so-called Islamic State also becoming active.

The Australian National University's William Maley - regarded as one of the world's foremost experts on Afghanistan - said the current security situation was "fairly alarming" and pointed to a United Nations report released on Sunday that found at least 36 civilians and pro-government fighters who had surrendered were executed earlier this month by a mix of Taliban and apparent Islamic State fighters.

"What this demonstrates is that the Afghan state is still not capable of providing ambient security for people whom the armed opposition might wish to attack," he said.

This might cause them to lose faith in the government and further undermine its legitimacy in the eyes of the population, he said.

Mr Trump's key challenge was to "affect the psychology of the situation in Afghanistan" by putting forward a credible strategy. In a country such as Afghanistan that has effectively been at war for decades, people tended to back "who they think will come out on top", he said.

Ending Pakistan's sanctuaries, to which the Taliban can retreat to regroup whenever they are under pressure, was the most important part of that, he said.

Importantly, Defence Secretary James Mattis said on Monday the plan was "a South Asia strategy ... not just an Afghanistan strategy" - a possible reference to Pakistan.

Defence expert John Blaxland agreed the Pakistan sanctuaries needed to be shut down but added that ending corruption and opium poppy farming - which provides significant revenue to the Taliban - were also critical.

But he said that "US leverage is much less than it used to be" because Pakistan had grown closer to China.

On international troops' presence, Professor Blaxland said Mr Trump needed to avoid predecessor Barack Obama's mistake of signalling his 2009 troop increase was temporary, meaning the "Taliban could just wait it out".

"It will be couched in terms of a similar posture to what the US has maintained in Japan, South Korea and during the cold war in Germany, a force that is maintained with no end state," he said.

Various options have been under consideration for Afghanistan, including sending about 3,800 more troops to augment the 8,400 already there to train and assist local forces.

Another option Secretary Mattis has mentioned is to replace US troops with private contractors.

Mr Trump met at Camp David on Sunday with more than a dozen aides, including Secretary Mattis, Secretary of State Rex Tillerson, national security adviser H.R. McMaster and Vice President Mike Pence.

- with the Washington Post