I understand that Agile team should be self organized and self driven,

but is there a provision that I can have someone who will allot tasks to developers and ensure that all user stories will be completed on time??

For example if there are two persons in an agile team who are not self motivated to take up tasks and they will work only when task is assigned to them with a deadline, how can we deal this in Agile?

The problem I face is that no one is fixing the deadlines for the tasks and the team is under delivering for the last two sprints. It will be better if we can have someone who can fix deadlines. IS there a provision for this in Agile