Kurdish Lobby Australia president Eziz Bawermend said Mr Trump's decision sent a message to the world that his administration would "run away" from a fight and desert its allies.

Mr Bawermend said Prime Minister Scott Morrison should join efforts at the United Nations to warn Turkey against invading Kurdish territory, while Australians themselves could "boycott" Turkey and Anzac Day commemorations in Gallipoli to make the same point.

After years of fighting against Islamic State, the Kurds are now exposed to attacks from Turkish forces expected to move into northern Syria in the wake of the US withdrawal.

"It is a total and complete betrayal of the Kurdish people," said Mr Bawermend, who was born and raised in Kurdistan but emigrated to Australia as a teenager and lives in Sydney.

"They have made huge sacrifices in fighting ISIS, which we see as a scourge of humanity, and those sacrifices include 11,000 dead and over 20,000 seriously wounded people who will no longer be their families' breadwinners.

"The Kurdish people of that region engaged in this war against ISIS not just to protect themselves but also, we believe, to protect the whole civilised world from ISIS's evil."

Defence Minister Linda Reynolds and Labor defence spokesman Richard Marles made no criticism of Mr Trump's decision on Tuesday, although Greens leader Richard Di Natale criticised the "erratic and dangerous" decision.

Weeks after Mr Morrison signalled his closeness to Mr Trump at a rare state dinner at the White House, Mr Bawermend said Australia should heed the signal from the President's sudden decision on Syria.

"Donald Trump has I think sent a signal to friends and foes that US administrations, as distinct from the American people, cannot be trusted, that when things get tough they will simply pack up and go away - if not run away," he said.

"I think that is an awful signal to give to the enemies of freedom, the enemies of peace, and it will encourage an awful lot of people around the world knowing that US administrations cannot be trusted and are not worth counting on."

"But I must emphasise the distinction between the President and the American people."

While the Kurdish community has been gratified by the support from ordinary Americans and Australians, it fears an invasion by Turkish forces under orders from Turkish President Recep Erdogan.

"We expect a bloodbath. The reason for Erdogan going in to Syria is not to fight terrorism - the main objective for wanting to invade Syria is a demographic change, to change the population along the border," Mr Bawermend said.

Senator Reynolds argued on Tuesday it was too early for the Australian government to respond to the US decision, but the Kurdish community wants Mr Morrison and his government to speak up against an invasion.

The Abbott government sent forces to drop munitions and humanitarian aid to Kurdish fighters in 2014, given the partnership between Kurdish and US forces against Islamic State.

Mr Bawermend said Australia could respond in two ways.

"Firstly they should tell Turkish leaders that the policy that the Turkish government is pursuing is barbaric, is inhuman and is not acceptable in this day and age," he said.

"The second avenue is to raise the matter at the United Nations General Assembly or Security Council.

"They should raise concern that the second largest army in NATO is planning, openly, to invade a sovereign member state of the UN to attack very lightly armed militia who have come into being to protect people's lives from the scourge of humanity that is ISIS."