You don’t want to upset the other person. You want to avoid an awkward situation.
But you might disagree with them. You might not want to say “Yes”.
So buy yourself some time.
Take a moment to listen to them. Explore where they’re coming from. Reflect back what they’ve said and the outcome they’d like.
Then, tell them what success looks like for you. Explain the outcome you’d like. Tell them you want to find a solution that works for both of you.
Do this and you’ll make it clear that you don’t agree. But you haven’t actually said “No”. And importantly, you haven’t said “Yes” either.