US actor John Lithgow is reportedly set to take on the role of Dumbledore as the makers of the new Harry Potter TV series start to assemble their cast.

The veteran Oscar-nominated star is "in final talks" to sign up to play the Hogwarts headmaster, according to film and TV industry outlets Variety and Deadline.

Lithgow is known for starring in sitcom 3rd Rock Rrom the Sun, with other roles ranging from voicing Lord Farquaad in Shrek to playing Winston Churchill in The Crown.

If his casting is confirmed, he will follow in the footsteps of Richard Harris and Michael Gambon, who played Albus Dumbledore in the Harry Potter films.

The TV series will feature a brand new cast and is expected to start filming this summer.

It will be "a faithful adaptation of the iconic books" by author JK Rowling, and is due to last for a decade, streaming service HBO Max has said.

No actors have yet been officially confirmed, but an open casting call has been held to find the three young stars.

"We appreciate that such a high-profile series will draw a lot of rumour and speculation," HBO told Deadline, in response to the reports about Lithgow.

"As we make our way through pre-production, we will only confirm details as we finalise deals."

He's been one of the most popular and respected actors in America for several decades, with roles that span both drama and comedy.

Lithgow earned two Oscar nominations in the 1980s (for The World According to Garp and Terms of Endearment) and won three Emmys for playing Dick Solomon in 3rd Rock from the Sun from 1996 to 2001.

He won another Emmy and got a Bafta nomination for playing Churchill in Netflix's The Crown - proving he can master a British accent - with more memorable TV roles in Dexter and Perry Mason.

He has recently been seen as an FBI boss in The Old Man, and as a scheming cardinal in Conclave, which is up for a string of Oscars this year.

The 79-year-old has the required combination of gravitas, warmth and levity to make a success of the Dumbledore role, although if the series does last for a decade, he'd be almost 90 by the time it ends.