Harmison took nine wickets in Paarl despite some problems

Harmison has not played for England since June, when a hernia problem brought an end to a run of poor form.

He took nine wickets for South African team Highveld Lions in an attempt to prove his return to form and fitness.

Moores told BBC Radio Four: "Hopefully he's going to come and join us. I don't think this is a make-or-break tour."

Harmison's progress in Paarl was monitored by England bowling coach Ottis Gibson, who saw him collect figures of 6-91 and 3-78 against Cape Cobras on a slow wicket.

He has one further match of domestic cricket to play, and is then expected to be added to a squad already featuring four specialist seamers - James Anderson, Matthew Hoggard, Ryan Sidebottom and Stuart Broad.

Sri Lanka will be a tough, short tour, we need everybody to be ready to go at the start of that trip England coach Peter Moores

Harmison himself said he had "sprayed it a little bit" in Paarl, where he sent down 14 wides in the first innings.

Lions bowling coach Gordon Parsons was impressed, though, telling BBC Radio 5 Live: "Having not bowled since July we couldn't have expected more than we got.

"It was a bit of an up-and-down first innings in Paarl but he ended up with six wickets.

"Then in the second innings he was much better and he looked the business.

"The standard of cricket here is very good and it's an indication that he can do well in Sri Lanka."

Moores explained: "He's in South Africa to prove three things.

"Physically, can his body take bowling in competitive cricket?

"Secondly can he get that bowling fitness he needs and, finally, can he be in the form he'll need to be in Sri Lanka?"

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"He had a tough last season.

"He struggled for form early on, then started to find some form, then got injured and missed the rest of the season, which was obviously disappointing for him.

"This is the reason why he is in South Africa now - he hasn't bowled competitively for quite a long time.

"Sri Lanka will be a tough, short tour, we need everybody to be ready to go at the start of that trip."

The Test series, which starts in Kandy on 1 December features three matches in as many weeks.