We have a clear play on words with the "I AM" phrase in verse 14 ("I will be" and "I am" are the same word in Hebrew). The "I AM" is with Moses. Moses' assertion that he cannot do this task is correct but entirely beside the point. He (Moses) is not doing the saving. Moses says, "I cannot do this." Yahweh responds, "You're not, I am."
--Peter Enns, page 101
