Pronunciation of "with" in phrases like "I'm with you"

"With" can be pronounced [with] or [wiTH], where [th] is the sound in "thin", and [TH] the sound in "this".

However, I've recently read in the Collins COBUILD English Dictionary for Advanced Learners that "with" can only be pronounced [wiTH] in phrases like "I'm with you" or "She's been with him".

I asked Raymond Weschler (webmaster at http://www.eslnotes.com) what he thought about this. Raymond is American.

Here is his answer:

----I think both are fine in all contexts, and in fact different speakers
use both. Individuals are always using slightly different pronunciations for
common words, especially if the difference is just a question of a consonant
being voiced or unvoiced (I've been made aware of the fact that I personally
say "if" as /iv/, which is not something I'm particularly proud of, but few
notice and none care).

The word "us" is pronounced with [s] at the end. The consonant is voiceless. That's the dictionary pronunciation and that's what I hear all the time.

But Ringo Starr of the Beatles, in at least two Beatles songs, sings "us" with [z] at the end. The songs are: "Yellow Submarine" and "Octupus's Garden".