Warren Gatland has hailed Wales captain Alun Wyn Jones' "unbelievable" international career as he prepares to break the world Test match appearance record.

Jones will overtake New Zealand World Cup-winning skipper Richie McCaw's 148 Tests when he leads Wales against Guinness Six Nations opponents Scotland on Saturday.

It will be the 35-year-old's 140th Wales appearance, in addition to nine British and Irish Lions Tests across their last three tours to South Africa, Australia and New Zealand.

Current Lions head coach Gatland worked closely with Ospreys lock Jones during a 12-year reign as Wales supremo, which included appointing him captain.

Jones made his Wales debut in 2006 and has helped his country win four Six Nations titles, three Grand Slams and reach two World Cup semi-finals.

"I am not surprised that he has reached this milestone, and I am also not surprised by the longevity of his career," Gatland said.

"He is unbelievably respected by the players – the example that he sets at training, the high expectations that he has on himself.

"At training you will call a lineout or a scrum or a next play, and he runs off and he is the first one there setting the example.

"That honesty really comes through with his own performances. He doesn't hide away from anything, and that's why he has so much respect from the players, and what I admire about him is he still never takes the jersey for granted.

"He is an unbelievable competitor. He's smart in the way that he plays, and that experience of knowing when to go hard in terms of kick-chase, the physicality that he brings in the contact area and the breakdown. He leads very much by example.

"I admire him because he is comfortable having different ideas, he's comfortable challenging others and challenging myself when I was coaching and disagreeing with me.

"I didn't always agree with him, but you know he is very much his own man, and I think that's one of the strengths that he has and he's brought to that Welsh team."

Gatland continued: "It's an amazing accolade to become the world's most capped player, particularly from a small nation like Wales.

"How long he can keep going for? I don't know. How many more caps could he potentially have? Maybe another 10 or 20.

"He might get through the next year and think, 'If I look after myself, manage myself well, I can make it to France (World Cup) in 2023'. Or, like a lot of players who are in their mid-30s and thinking about the future, one day the light bulb might turn on and say, 'I've achieved everything I wanted to do, and it's time to retire'.

"So we will wait for that day when he does decide to call it quits, and I am sure that we will celebrate what has been an unbelievable career internationally.

"I think he has got ambitions for next year with the Lions. It (second row) is a position with a huge amount of quality and depth, and that's going be a challenge for him.

"It is important that he has a good Six Nations, he will know that, but if he does end up in South Africa in 2021 it would be his fourth Lions tour, which is an incredible feat."

Wales' record international points-scorer and current national squad skills coach Neil Jenkins has worked with Jones since his time as an under-21 international.

"He plays in the front five, and it is one of the hardest positions you could possibly play on a rugby pitch, yet he still seems like he is a young kid, if you ask me," Jenkins said.

"He turns up to training, he's first to everything. Very rarely does he get beaten at anything, if he does at all. That's the way he is.

"He's just world class. He is one of the best to ever have played the game, and he is going to beat someone that is maybe the greatest player, who knows?

"I would like to think he has got a fair bit in him yet, but when the day does come when he is not wearing that Wales jersey, he will be sorely missed. He has been huge for Wales.

And flanker Justin Tipuric, a long-term colleague of Jones for Wales, Ospreys and the Lions, told the PA news agency: "I don't think words do justice to Al.

"I get lucky in that I get to train with him every day. He never seems to stop. He is a machine, and he deserves everything he gets."