The Nine and the Three

[Inziladun]

While looking back on what I believe was the first thread (http://forum.barrowdowns.com/showthread.php?t=1907) I ever started, I had another thing I was considering that is a bit far afield of that, but the mentions of the Unfinished Tales chapter The Hunt For the Ring there perhaps bring it in line.

Anyway, in that section, when detailing the Nazgûls' search for the Shire around the Gladden Fields and to the north, the Witch-king has the thought that the land of the Halflings might well be

....not far from the hated land of Lórien....if it was not indeed within the fences of Galadriel. But the power of the White Ring he would not defy, nor enter yet into Lórien.

Would not defy seems to imply that the WK knew for a fact that Galadriel was the keeper of Nenya, and that he chose not to challenge her. However, FOTR leaves little ambiguity that Sauron did not have firm knowledge of who kept the Three, though he had suspicions. Maybe that bit about the Witch-king was a mere slip on the part of Tolkien. It certainly seems that if the Nazgûl were capable of perceiving the presence of the Three, there had been ample opportunities to do so.
For instance, Elrond probably used the power of Vilya when he caused the Bruinen to flood. And the Nazgûl attacked Gandalf on Weathertop, so one would think that Narya would have made its presence known, if they could have felt it.

So I guess the question is, could the Nazgûl, being under the power of the Nine Rings, feel the proximity of other Rings of Power besides the One? If not, why not?

[Zigûr]

However, FOTR leaves little ambiguity that Sauron did not have firm knowledge of who kept the Three, though he had suspicions.
I think this is the salient point. Logically speaking, there were only three places where the Three could be kept: Rivendell, Lórien and Mithlond - anywhere in which the Noldor still lingered. Sauron didn't know where the Shire was until Saruman told the Lord of the Nazgûl, which suggests to me that he had not necessarily spied out the West sufficiently to know, for instance, that Círdan no longer possessed one of the Three.
My point is that, according to Sauron's wisdom, to whom would the Three have logically been allocated? Lórien was the closest to both Moria and Dol Guldur, and resistant to assault, which implies a Ring being present at that location. If Sauron knew or at least suspected that Gil-Galad held some of the Rings prior to his death, I think it would make sense, by his logic, that he had passed the greatest of them, Vilya, to one of his subordinates - Elrond or Círdan. That leaves Narya and Nenya to be accounted for.
Despite the fact that he himself did not have a hand in creating them we could also imagine that Sauron was aware of the respective properties of the Three. Depending on the circumstances, this may have led him to at least be able to take an educated guess as to Nenya's location.
I personally don't believe that the bearers of the Nine could detect the location of the Three - it doesn't seem to make sense to me that Sauron could be unaware of their location, yet his lieutenant could. I would venture, personally, that it was more of an accurate supposition deriving from a combination of evidence and guesswork based on his knowledge of the Rings.
Similarly the mention of the White Ring could be an elaboration on the part of the author deriving from superior later knowledge, and so Sauron might have been aware, or could hazard a guess, that one of the Three was in the Golden Wood without being sure which one.
Personally I think that the secrecy surrounding the Three was a last-resort safeguard on the part of their bearers, because I think it must have been completely obvious to Sauron which locations in the West held Elven-rings even if he could not be sure where each individual Ring was located.