This paper presents optimal resource allocation for multi-target tracking with a phased array radar. To fully exploit the radar potential, the resource manager must allocate resource to tasks in a way which maximises performance. Especially, the track tasks are required to be executed to consider expected tracking performance while utilizing limited time resource. Thus, in this paper, we propose sequential resource allocation algorithms for multiple track tasks that ensure optimality under a justifiable convexity assumption. The proposed algorithms are validated on a ballistic objects tracking example.