In light of the complexity of high-risk AI systems and the associated risks, it is important to develop an appropriate conformity assessment procedure covering the different lifecycle phases of AI systems, including their design and development. For high-risk AI systems related to products that are covered by existing Union harmonisation legislation based on the New Legislative Framework, the conformity assessment of those AI systems should, as a general rule, be assessed as part of the conformity assessment already provided for under that law. It is therefore necessary to ensure consistency between this Regulation and existing Union harmonisation legislation.