Leigh Griffiths is set to pledge his future to Celtic for the rest of his career.

Sportsmail understands MLS side Sporting Kansas City had a £5million bid turned down by the Scottish champions in January and Griffiths and his representatives have since been locked in talks over a new contract.

Those discussions are now edging towards a conclusion and the Scotland international forward admitted he will be delighted to become a Celt for life.

Celtic's Leigh Griffiths launches the clubs new away kit for the upcoming 2018-19 season

'We are inching further forward towards a new deal,' Griffiths said. 'It's getting closer and there's not far to go now. We are about 85 per cent done.. There's just a couple of tweaks needed.

'It won't be a weight off my mind because I've still got two and a bit years to go on my current deal.

'But the fact that the club are even talking about a new contract gives me joy and delight that I am going to be here for basically the rest of my career. When it does get done and signed I will be delighted. I see my best years as being at Celtic.'

Griffiths remains is well aware of the many challenges that lie in wait next season. First up is the tightrope of the Champions League qualifiers that need to be negotiated with care.

After that comes the prospect of a tooled-up Rangers under new manager Steven Gerrard making a better fist of a Premiership title challenge than they managed last season.

Yet Celtic's record capture of French striker Odsonne Edouard from Paris Saint-Germain, in a deal that could reach £9million, represents a clear and present danger to his chances of starting regularly for Brendan Rodgers' team.

The striker turned down a move to the MLS in January and is ready to commit to Celtic for life

With all that in mind, Griffiths has declined a summer holiday, instead spending his pre-season break under the knife then in the gym.

Now fully fit and raring to go, he is hoping to put his stop-start last campaign behind him to play a central striking role.

'I didn't go anywhere over the summer,' said Griffiths.

'I just had a wee tidy up hernia operation and, after a couple of weeks' rest, I was back in the gym working on my fitness.

'The op was my reason for not going away with Scotland to Peru and Mexico but I spoke to Alex McLeish about it and he was fine. He wants me fit and ready for September to fire us in the qualifiers.

'I've given myself plenty rest and I've spent a lot of time with my kids. I'm a home bird anyway. I like being around my family and kids. It's difficult enough to take them out of school and away. But I feel I've had a decent enough break and I'm ready for the new season.

Griffiths (right) poses with Callum McGregor at the launch of the club's new away kit

'Last season was frustrating. Injuries were keeping me out but hopefully I am injury-free now and that I get a good pre-season under my belt and come through it with flying colours. But I'm fit and ready to go.

'Do I expect a greater challenge next season from Rangers under Steven Gerrard? It's not just them. If you look at last season, Hibs finished strongly.. Aberdeen will be up there fighting again. Hearts have added to their squad. The league is getting stronger every year and we relish the challenge.

'And (with the permanent arrival of Odsonne Edouard) we have competition for places up front.

'It is a great addition to the squad. But whoever starts the season will have a dip at some stage. Whenever I get my chance I have to take it.' Grifiths also turned his attention to the 40 degree heat that awaits in Armenia when Celtic take on Alashkert in the Champions League qualifiers next month.

Citing the conditions as a factor when Celtic lost 1-0 in Gibraltar to Lincoln Red Imps two summers ago in Rodgers' first match in charge of Celtic, he insisted his side are experienced campaigners now.

'Gibraltar was one of the hottest matches I've played in' he said. 'I know no-one wants to remember that night but the conditions, the heat, the pitch.. Everything went against us.

'But we've since been to Kazakhstan and Israel in difficult conditions.

'We just need to get the job done and we will need to adapt to the conditions.

Griffiths is relishing another testing challenge in the Champions League qualification rounds

'Of course we'd like a decent result in the first leg but, with the crowd behind us at Celtic Park, we have a chance of getting the job done in the second leg.' Alashkert have moved the game to 16,000-capacity Yerevan Stadium and vowed to let fans in for free to turn the heat up on Celtic even further next month.

But Griffiths, who was pelted with missiles, including a Buckfast bottle, during last summer's qualifier against Linfield in Belfast, won't be fazed.

'I was praying we didn't get (Linfield) again,' he smiled. 'I am not sure I would have got in and out without a police escort. But whether we play in front of 100 fans or 10,000 fans we will just focus on getting the job done.'

A member of Celtic's unprecedented double-treble winning side last season, Griffiths is hoping to join another exclusive club in the forthcoming campaign.

Should the 27-year-old find the net just twice more for Celtic he will have reached 100 goals for the Scottish champions since signing from Wolves in 2014.

The last Parkhead centurion was John Hartson in 2005 when he joined a celebrated group of players including legendary figures like Henrik Larsson, Kenny Dalglish, Jimmy McGrory, and Bobby Lennox.

And Griffiths joked if he doesn't join such esteemed company in the next 12 months he would be best retiring from the game.

'I'd like to get to 100 goals. If I don't get to that mark next season then I may as well quit football,' he laughed.

*Leigh Griffiths was speaking at the launch of New Balance's new Celtic away kit for season 2018-19.*