From the POV of your team lead, this is perhaps not an advantage move on his side, so I do understand his concern, after all he is not the company, just an employee as you. And from your description it seems that you are a competent employee, thus even the less

Nevertheless he should give a more encouraging answer as a team lead. And if you still want to make the change (looks like you are not very interested in it too), maybe just ask to spend a little more time on server stuffs and see what's the reply.

It's all negotiation and sometimes it's difficult to ask the right question.