I would translate it more beautifully and poetic as "Я хочу сделать всё что в моих силах, потому что ты единственный". This is my personal human translation. If you want to use an online automatic translator, I would recommend to look at this one http://learningrussian.net/translator.php

I would like to suggest one small change to Olga's otherwise excellent answer: Всё невозможное хочу я сделать, так как ты единственная моя. I used the first person of the verb хотить to reflect the exact wording of the question. I also used the feminine form of "the only one" because in my mind these words are usually spoken by men.

Всё невозможное могу я сделать, так как ты единственный-единственная моя-мой.

First, why are you guys asking for some translation without providing a little bit context to it???? Who are you talking about? What's the situation? ... etc. Just interesting enough Who did give Olga's answer a thumb down?? Are you guys actually speaking Russian, I guess not )) Second answer it's just a word-to-word translation, if you need to understand every word it's ok but it doesn't sound good in russian.

я хочу сделать все невозможное, потому что ты единственный :)