Prime Minister Malcolm Turnbull has praised President Donald Trump for winning a vote that marks a major step towards dismantling Obamacare.

Mr Turnbull began his remarks at a commemoration dinner marking the 75th anniversary of the Battle of the Coral Sea by congratulating the president on his bid to roll back Barack Obama's signature health care law that aims to provide affordable health care.

"Well done, congratulations," Mr Turnbull said.

"It's always good to win a vote in the Congress, or the parliament as we call it," he said.

"I got to say, it's always satisfying to win a vote when people predict you’re not going to win it too.

"So keep at it, it's great.

But moments before Mr Turnbull’s remarks, Mr Trump praised Australia for having a better health care system than the United States.

“We have a failing health care system, I shouldn’t say this to our great gentlemen and my friend from Australia,” Mr Trump said.

"You have better health care than we do."

Australia's publicly funded health care system is similar to what Mr Trump is trying currently trying to dismantle, a fact former presidential candidate Bernie Sanders was quick to point out.

The newly introduced Obamacare repeal would take away the requirement for health insurers to cover people with "pre-existing conditions".

That includes people with diabetes, autism, heart problems or a history of cancer.

Survivors of rape and domestic violence are also considered to have a "pre-existing condition".

The repeal is also expected to jack up prices for older and sicker Americans, and also includes a tax cut for the very wealthy.

Earlier, Mr Trump called the vote an "unbelievable victory" as he gathered with Republican representatives in the White House Rose Garden, vowing to "finish off" Obamacare.