A new resource joined an iterative project team but is not completing deliverables on time. How should the project manager address this performance issue?

The project manager should coach the new team member to address the performance shortfall. In an iterative environment, coaching is a primary responsibility of the project manager (or Scrum Master) to help team members improve and become self-organizing. This approach fosters growth, addresses the root cause of the issue, and aligns with agile principles of continuous improvement and servant leadership. Discussing with the resource's manager might be necessary if coaching fails, but it's not the first step. Providing feedback during a retrospective is too late and less personal; immediate, direct coaching is more effective for individual performance issues. Asking the sponsor for a replacement is a drastic measure that doesn't address the current team member's development and should only be considered after other interventions have failed.