England captain Jos Buttler says he is "100 per cent" fit for the T20I series with Australia after recovering from a calf injury.

Buttler suffered the injury while playing in the Hundred in August and did not take part in England's series win over Pakistan.

But he returns on Sunday against world champions Australia, where they will play three matches ahead of the World Cup.

"I'm back to 100 per cent," Buttler said. "Had a good time in Pakistan rehabbing, probably could have played earlier, but with the World Cup around the corner, it was the right thing to do."

Buttler is expected to open with either Alex Hales or Phil Salt, and he is confident in England's batting capabilities.

"We have great options at the top of the order with guys in really good form in Pakistan," he added.

"They're both excellent options. Whoever I partner with will have a great go at it."

Buttler also revealed that Liam Livingstone is a doubt for the World Cup, starting later this month.

He explained Livingstone is "a little way off at the minute", saying: "Hopefully he'll get back to full fitness before the start of the World Cup."