In a situation where there is disagreement about the value of certain activities in a project, especially when the project is at risk of running over budget, the project manager should:

Collaborate with the functional manager to determine which critical activities could be accommodated by the budget (A): This approach allows for a shared understanding of the project’s constraints and priorities. It also provides an opportunity for the functional manager to contribute to the decision-making process, which can lead to better buy-in and less resistance1.

Conduct a meeting with the functional manager to explain why the activities needed to be stopped ©: Clear communication is key in managing conflicts. By explaining the reasons behind the decision, the project manager can help the functional manager understand the situation better. This can lead to a more constructive discussion and potentially a compromise1.

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https://www.pmbypm.com/conflict-management-strategies/