Moeen Ali's England exile will stretch into 2020 with national selector Ed Smith admitting he does not know if the all-rounder will return to the international arena.

England named a 17-man squad on Saturday for the four-match Test series in South Africa, which starts on Boxing Day, featuring recalled trio James Anderson, Jonny Bairstow and Mark Wood.

But Moeen was again conspicuous by his absence, just weeks after England captain Joe Root had hinted that the 32-year-old was in contention for a Test recall in South Africa by saying he "adds a different dimension" when firing on all cylinders.

Moeen asked for and was granted an indefinite sabbatical from Test cricket shortly after being dropped from the Ashes squad following a torrid time in the Edgbaston opener, while he has since lost his red-ball central contract.

At the time of his axing, Moeen was the world's leading Test wicket-taker over the previous 12 months – but Jack Leach has now taken over the mantle of England's leading spinner.

"We've had to make plans for this tour without Mo," Smith said.

"In an ideal world we would like Mo to be available but we have to deal with the situation as it is.

"We respect that and we hope he will return to be available sooner rather than later.

"At this stage we don't know when he will return to being available for Test cricket. It's my hope that he does return to being available.

"We all know Mo is a talented and valued cricketer for England. At the moment we just don't know if and when that might happen."

Smith, however, said that Moeen remains committed to playing for England.

"When I spoke with Mo I was keen to talk about cricket issues, find out where he was at with his cricket," he said.

"He did say he thought there was more Test runs and more Test wickets in him. That was encouraging and that's what we believe.

"We'll be keeping in regular touch with Mo in the next weeks and months.

"At the moment there's no time frame but from my point of view, and the selectors' point of view, the sooner he's available the better."

Anderson, England's record wicket-taker, has been recovering from a calf injury which kept him out of most of the Ashes.

Both Anderson and Wood have been working with coaches Glen Chapple and Neil Killeen in a bid to hit the ground running when the tour starts with a warm-up match against a South Africa Invitational XI on December 17.

Durham quick Wood has not played Test cricket since February and has been recovering from a left knee injury and side strain sustained during the World Cup final in July.

"James hasn't completed a game since the injury but the evidence we have seen in front of us is very encouraging that he'll be able to play a full part in the tour," Smith said.

"Mark has progressed well but the medical advice is he's unlikely to be fit for the start of the tour.

"The plan and the hope is for him to available at some stage."

Bairstow was dropped for the New Zealand series defeat after averaging 23.77 during this summer's Ashes.

It was a move that backfired when newcomer Ollie Pope had to deputise behind the stumps for the second Test in Hamilton after Jos Buttler sustained an injury.

"Jonny Bairstow playing well can get into the England team in a number of different positions," Smith said.

"Sometimes in careers it's not bad for players to work on something specific, reset, perhaps have some new goals, perhaps have some time in a new coaching context.

"We've seen in a number of situations that can help. The message from him was loud and clear he wanted to get back in the team."

England squad: Joe Root (Yorkshire, capt), James Anderson (Lancashire), Jofra Archer (Sussex), Jonny Bairstow (Yorkshire), Stuart Broad (Nottinghamshire), Rory Burns (Surrey), Jos Buttler (Lancashire), Zak Crawley (Kent), Sam Curran (Surrey), Joe Denly (Kent), Jack Leach (Somerset), Matt Parkinson (Lancashire), Ollie Pope (Surrey), Dominic Sibley (Warwickshire), Ben Stokes (Durham, vice-capt), Chris Woakes (Warwickshire), Mark Wood (Durham).