Please reply as soon as possible.
委婉点的：I look forward to your prompt reply.
I look forward to hearing from you as soon as possible.
I should appreciate it if you could reply as soon as possible.
I await your prompt reply with great interest.
Please reply as soon as possible.
委婉点的：I look forward to your prompt reply.
I look forward to hearing from you as soon as possible.
I should appreciate it if you could reply as soon as possible.
I await your prompt reply with great interest.