"We remain confident always that we will be in," De Klerk told the media on Thursday.
"There is an immense amount of work that is taking place behind the scenes."
He made these comments ahead of the SA Rugby Union's (SARU) general council meeting on July 13 in Cape Town, where a decision will be made on the participation of South African teams in next year's Super Rugby competition.
SARU's executive committee proposed at a special general meeting in January that the top four teams in the South African conference in this year's Super Rugby competition would join the Southern Kings in next year's competition.
The Kings have been guaranteed a spot in the 2013 season's SA conference, while the participation of the other four teams still had to be decided.
It was proposed that the last-placed team in the SA conference would play a promotion/relegation match against the non-Super Rugby franchise after the 2013 and 2014 season.
With the Lions languishing in 14th place on the overall log, they are the likely candidate to be relegated at the end of the season, if the above proposal is ratified at the general council meeting.
De Klerk, however, said there have been guarantees that the Kings' participation would not be at the expense of the current franchises.
"If we listen to what was said at the sport portfolio committee... the Southern Kings will play in 2013, but not at the expense of any other side," De Klerk said.
"So we are listening to that and we understand what is going on. There is some big lobbying taking place and I do believe that we will still remain in this competition for 2013."
SARU chief executive Jurie Roux told Parliament's sport portfolio committee in May that the Kings' inclusion should not happen "at the cost of SA Rugby or any of the other franchises".
There had also been rumours that players were looking for contracts elsewhere, given the uncertainty of the team's participation in Super Rugby.
De Klerk, however, dispelled these rumours on Thursday, saying the union had secured most of the players for the next three years.
"We are aware of what had take place the last while, the coming and going of equity partners," said De Klerk.
"We've secured additional sponsors. We've locked in our players all secure for 2015."
The Lions play the Stormers in a Super Rugby clash at Newlands on Saturday. Kick-off is at 17:05.
Teams:
Stormers:
15 Joe Pietersen, 14 Gio Aplon, 13 Juan de Jongh, 12 Jean de Villiers (captain), 11 Gerhard van den Heever, 10 Peter Grant, 9 Dewaldt Duvenage, 8 Siya Kolisi, 7 Don Armand, 6 Tyrone Holmes, 5 Andries Bekker, 4 De Kock Steenkamp, 3 Frans Malherbe, 2 Deon Fourie, 1 Deon Carstens
Substitutes: 16 Tiaan Liebenberg, 17 Brok Harris, 18 Quinn Roux, 19 Jebb Sinclair, 20 Louis Schrueder, 21 Burton Francis, 22 Bryan Habana
Lions:
15 Andries Coetzee, 14 Deon van Rensburg, 13 Lionel Mapoe, 12 Butch James, 11 Anthonie Volminck, 10 Elton Jantjies, 9 Tian Meyer, 8 Joshua Strauss (captain), 7 Grant Hattingh, 6 Derick Minnie, 5 Franco van der Merwe, 4 Hendrik Roodt, 3 Jacobie Adriaanse, 2 Callie Visagie, 1 JC Janse van Rensburg
Substitutes: 16 Martin Bezuidenhout, 17 CJ van der Linde/Ruaan Dreyer, 18 Ruan Botha, 19 Jaco Kriel, 20 Michael Bondesio, 21 Waylon Murray, 22 Ruan Combrinck