I also worked in similar environments where sales people already promised unrealistic deadlines to customers. But you have to know the 3 weeks is not your deadl

I also worked in similar environments where sales people already promised unrealistic deadlines to customers. But you have to know the 3 weeks is not your deadline, you said 2 months, it's the lead's deadline, he is just trying to shove the hot potato on your lap. There's a great quote for this: "Bad planning on your part does not constitute an emergency on my part".