Manchmal sagt er das, aber nur fast.
I have never once seen a translation book teach "ich hab e dich lieb" but they should.
— Sep 2 '11 at 23:40•.
It is the unambiguous declaration of love.
Interesting you ask that, since I experienced the exact same confusion even though being a native German - over 10 years ago, a girl I loved said "Ich hab dich lieb" to me and meant "Ich mag dich sehr gern", but I understood it as "Ich liebe dich".
I was born there … learned German first and then learned English.