Niki Lauda will return to F1 when he is ready.

That is the news from the F1 legend's son Mathias. Earlier, Lauda - who turns 70 on Friday - targeted his return to the paddock from a lung transplant for the Barcelona tests.

But he is not yet strong enough even to travel to Australia for the season opener.

However, Mathias Lauda told DPA news agency: "He is fighting like a lion.

"He wants to return to normal life as soon as possible."

But Mathias said his father no longer has a particular return date in his diary.

"There is no time limit, what is important is that his body returns to his old strength," he insisted.

Mathias admitted that a return for the start of the 2019 season is too soon, but "wait and see".