America's allies should not be guided by President Donald Trump's at-times erratic Twitter posts, according to former US General and CIA director David Petraeus.
In a message of reassurance, General Petraeus suggested people should "follow the money and follow the troops, don't follow the tweets".
"The overall way to characterise American foreign policy is more continuity than change."
In a 45-minute Q&A session as the key note speaker at the Liberal Council meeting on Friday night, he also encouraged Australia and its allies to stand up to China in the South China Sea and conduct freedom of navigation exercises.
The former CIA Director oversaw the US wars in Iraq and Afghanistan and is one of the most respected military leaders of his generation, though he was forced to resign in 2012 from his position as chief spy because of an extramarital affair.
General Petraeus also suggested Australia may have to take the lead in combating Islamic State in the Philippines. Fairfax Media revealed on Friday that RAAF spy planes are set to join the fight against Islamic State in that country.
The general described Malcolm Turnbull as a "war-time prime minister" and said he would have to grapple with when, and to what extent, Australia should intervene in regional disputes.
"There will be some [conflicts], like in the Philippines for example, where Australia will either lead or play a very significant or Mali, where the French took the lead, but you will still even their see very significant contributions from the United States."
He predicted "at least a generational struggle" against radical Islam, suggested the West would need to get used to "lone wolf" attacks as have in Melbourne, London, Paris and beyond and flagged the danger of a "virtual caliphate", and dispersed Islamic radicals around the world, once the Islamic State was defeated in Syria and Iraq.
"You can eliminate all the ground vestiges of this [Islamic State], and there is still going to be the internet."
Australia and its regional allies needed to be firm with China, which has built and then militarised artificial islands in the South China Sea within a so-called nine dash line area, General Petraeus said.
He called on Australia to follow the United States' example and conduct a so-called freedom of navigation (FONOP) naval exercise within the 12-nautical-mile zone around the islands claimed by China.
"We don't have to have brass bands and fanfare, but it should be done... and if it can be done as a coalition, it says much more," he said.
Freedom of navigation exercises are "hugely important..we have to be firm."
"The nine dash line is an outrageous assertion [of Chinese sovereignty over the South China Sea] that is completely without foundation in international law, as we found when the Philippines took their case to the world court and the case was decided in their favour."
He also suggested the Obama administration had made promises to sail or fly anywhere within the contested area but missed key opportunities to stand up to China.
"There were opportunities when those islands were first being constructed where we could have said ok, we will help the Philippines build theirs [islands], we will help Vietnam, and Malaysia wants to get in to the act."
Those three countries are among the nations contesting China's claim to sovereignty.
The general, who was at one point in the running for the jobs of Secretary of State and National Security Adviser in the Trump administration, critiqued the President on four key policy areas: pulling out of the Paris climate agreement, building a border wall between Mexico and the United States, and pulling out the Trans-Pacific Partnership trade deal.
The United States would likely meet its Paris emissions reduction targets regardless, General Petraeus said, but pulling out of the agreement sent the wrong message to international partners.
On the border wall, he pointed out that net flow of migrants between the two nations was currently towards Mexico.
The fourth issue was the continued "ambivalence about the US leading the rules-based international order".
"I do believe that the United States has to continue to exercise its leadership...we have a pragmatic president, he is someone who showed he will do what is necessary to get elected, and now he will do what he needs to do to be successful".
He outlined five lessons to be learned from the past 15 years in the Middle East in the fight against Islamic extremism.
1. Ungoverned spaces will be exploited by Islamic extremists. 2. "Las Vegas rules do not apply" - what happens in radicalised pockets of the world does not stay there, and violence and refugees are exported around the world. 3. In most cases, the US is going to have to lead, but partner with regional allies. 4. A comprehensive approach is needed - Islamic state and Al Qaeda can't just be defeated by drones strikes or special forces. 5. "We are engaged in a generational struggle."
