Saruman: The not-so wise?

[Tinman]

I have a few unanswered question about saruman's big picture. I'm mostly confused as to why he held the white council back for so long from attacking the necromancer.

It appears for quite some time, he'd been searching for the one ring, learning everything about ring lore he could, and even designing his own. Its hard to say when saruman fell to corruption...

We do know that he had wanted the one ring for himself, and that he was preventing the white council from looking too deeply into the activity taking place in mirkwood. My question is, why? He probably had an idea as to what was going on there... and unless we're watching the jackson films, he wasnt really in league witj the dark lord sauron. So what benefit could he have possibly hoped to gain from not taking out sauron before he was fully restored to power? if anything, he knew sauron would be the only other person (besides gollum, who im not certain he knew of yet), to be actively searching for the ring... which all the other wise believed to be lost forever.

So why hold back the siege of the necromancer? What could he possibly been hoping to achieve by allowing another power to come back, who wanted the same thing he sought?