Christian Lee retained the ONE lightweight MMA world title in his scheduled clash at the weekend in Japan. It did not take long for him to receive a challenge for the welterweight belt he also holds from Croatian sensation Roberto Soldic.'Robocop' called out 'The Warrior' to a title clash at welterweight on social media after Lee successfully retained the lightweight gold with a second-round TKO win over Turkish challenger Alibeg Rasulov at ONE 173: Superbon vs. Noiri on Nov. 16 at Tokyo's Ariake Arena.Following his victory, Christian Lee signified his intention to be more active next year and also defend the welterweight title in his possession.Soldic jumped on the opportunity to stake his claim for a shot at the world title, commenting on ONE Championship's post on Instagram on Lee's latest victory. View this post on Instagram Instagram PostThe UFD Gym affiliate wrote:"Congrats 🤝 let's go @christianleemma"Roberto Soldic calls out Christian Lee.Soldic was last in action in February, where he scored his first win in ONE Championship, knocking out Turkey's Dagi Arslanaliev in the opening round.Christian Lee earns $50,000 performance bonus for TKO win at ONE 173Christian Lee's TKO win over Alibeg Rasulov at ONE 173 also earned him a $50,000 performance bonus from ONE Chairman and CEO Chatri Sityodtong. He was one of five fighters who received the incentive on fight night.The 27-year-old Singaporean-American champion got the bonus with his dismantling of Alibeg Rasulov to retain the lightweight MMA world title.Lee's leg was taken down early by the challenger, who then wrapped his arms around the champion's legs in an attempt to keep the match on the ground. But Lee would have none of that, eventually scrambling his way out and engaging Rasulov on the standup with telling hits as the opening round progressed.In the second round, Christian Lee opened things with low kicks to stave off any takedown attempt by the challenger. The fighters exchanged punches before Lee connected a knee to the body and a high kick, which he used to unleash more strikes that rocked Rasulov.In an attempt to stymie Lee's attack, the Dagestan native made another go for a takedown to which Lee was ready for. The champion was able to trap his opponent with a D'Arce choke and uncorked a series of ground knees, which Rasulov had no answer to, forcing the referee to stop the contest at the 2:32 mark of the second frame.The win at ONE 173 gave a definitive ending to Lee's battle with Rasulov after their first encounter last December ended in a no-contest. Lee accidentally poked the eye of Rasulov in the second round, and the latter was unable to continue.