Independent MP Andrew Wilkie has questioned whether Syrian President Bashar al-Assad's regime was responsible for last week's chemical weapons attack on civilians that prompted US missile strikes.

Key points: Andrew Wilkie formerly worked as a senior intelligence analyst

Andrew Wilkie formerly worked as a senior intelligence analyst Mr Wilkie says he does not trust the Trump administration

Mr Wilkie says he does not trust the Trump administration He says "Australians should be cautious…and not too quick to automatically endorse US claims"

Mr Wilkie, a former senior intelligence analyst, said there was no doubt the attack occurred but Australia should not blindly accept assurances from US authorities.

His comments come after US Defence Secretary James Mattis said "there is no doubt" the Assad regime was responsible for planning and orchestrating the deadly attack.

"Frankly, I just don't trust the Trump administration," Mr Wilkie told Sky News.

"It would make a lot of sense for them to beat the drums of war again when they are under so much pressure domestically."

Sorry, this video has expired Wilkie says Australia should be 'more independent' from the US position on Syria

The Federal Government and the Labor Opposition have strongly supported the US military strikes, describing them as a necessary, proportionate and calibrated response.

Speaking in India, Prime Minister Malcolm Turnbull said it was clear the attack was conducted by the Assad regime.

"I am not going to go into intelligence that I have or have not seen ... [but] this was an attack that was undertaken by the Assad regime," he told Sky News.

But Mr Wilkie, who resigned from the intelligence agency Office of National Assessments in 2003 in protest over Australia's role in the Iraq War, said the Federal Government should have "learned from the past".

"I think we should be very cautious in Australia and not be too quick to automatically endorse what the US is saying," he said.

"We have been stuck in the Middle East quagmire since 2003, again on account of allegations of chemical and biological and nuclear weapons."

Mr Wilkie said he wanted to make it "absolutely clear" that Mr Assad could have been behind the attack, but said it seemed unlikely for a range of reasons.

"To be brutally honest, if you want to kill a hundred people it is far simpler just to drop a couple of high-explosive bombs from an aircraft on a village," he said.

"It's a very unlikely choice of weapon when you know it is going to attract such a strong military response from the United States.

"It's a very unlikely choice of weapon when you know it is going to complicate your relationship with your ally, Russia."

Earlier, US Defence Secretary James Mattis said there was "no doubt" the Syrian regime was responsible for the gas attack.

General Mattis said that if Syria were to use chemical weapons again it would "pay a very, very stiff price."