China's top diplomat is to meet an outspoken Australian ex-prime minister who has criticised Canberra's stance on Beijing, a move that threatens to overshadow efforts to improve troubled ties.

Foreign Minister Wang Yi on Wednesday will meet his Australian counterpart Penny Wong in Canberra, his first visit to the country since 2017.

While the whirlwind trip has been hailed as a sign of mending ties between the nations, Wang has ruffled feathers by scheduling a meeting with government critic Paul Keating on the sidelines.

Keating, who has long pushed for deeper ties with Beijing, said he received an "unexpected invitation" to discuss "international matters" with Wang.

"As a matter of courtesy, let alone anything else, I was happy to advise the Chinese Foreign Ministry that, given I had the time, I would be pleased to sit down and discuss international matters," Keating said in a statement on Monday.

Keating, who led Australia's Labor government from 1991 to 1996, has rubbished recent attempts to adopt a more assertive stance towards Beijing.

He has accused Foreign Minister Wong of trying to "rattle the China can" by painting Beijing as a looming military threat.

"What would be the point of China wanting to occupy Sydney and Melbourne? Militarily? And could they ever do it?" Keating said in a speech last year.

"The question is so dumb, it's hardly worth an answer."

The Australian government was on Tuesday trying to play down the significance of Wang's sit down with Keating.

"It's singularly unsurprising he would meet with a former prime minister, particularly one such as former prime minister Paul Keating, who has championed deeper ties with Asia," said senior cabinet minister Chris Bowen.

Opposition foreign affairs spokesman Simon Birmingham said Keating's support for China was "clearly welcomed for propaganda purposes elsewhere"