Treasurer Josh Frydenberg will go to Bali on Thursday for a meeting of G20 finance ministers and he will tell them the world can't afford the trade war between the US and China getting out of control.

President Donald Trump has slapped billions of dollars worth of tariffs on Chinese products and China has retaliated with similar tax hikes.

"To date there has been little macroeconomic impact as it has been confined to about two per cent of world trade," Mr Frydenberg told reporters in Sydney on Wednesday.

"But Australia is a big exporter. It supports nearly one in five Australian jobs.

"So my message to my fellow G20 finance ministers will be that free trade equals more jobs, free trade equals more investment and free trade means higher economic growth."

Former federal Labor treasurer Wayne Swan says countries such as Great Britain, Canada, Europe and Japan should speak out against the "incredibly disruptive" actions of the US on the global economy.

Mr Swan, who will also attend the Bali meeting, says Australia and developing Asian countries would bear the brunt of a trade war.

"We are all very interconnected. When something goes wrong in one area it can quickly spread if we don't have a decided and firm response from international authorities," Mr Swan told Sky News on Wednesday.

The International Monetary Fund on Tuesday cut its global growth forecast for 2018-19 by 0.2 per cent to 3.7 per cent, citing the negative impact of new US trade measures.

"It's even more important that countries like Great Britain, Australia, Canada, the Europeans, the Japanese speak out very clearly and succinctly about the importance of good policy," Mr Swan said.

"When you see the state of politics and policy in the United States and its actions, which are incredibly disruptive to the established global order."

Australian Associated Press