There was some debate and objections in Congress and Senate about potentially expanding NATO, even if warranted as a necessary stop-gap against future Russian bullying and aggression due to the fact that Russia, in the late 90's and even early 2000's under Putin was significantly weaker militarily and economically then what it became or is now. If Russia wasnt a significant threat or stood to become one again from some geopoliitical experts standpoints of 1997-98, why expand NATO just because we're concerned of what Russia might evolve into over the next 10-15 years?
From the context of late 90's and also given added factors that Russia was still severely weak recovering from economic sanctions, a brutal seperatist campaign/civil war going on in Chechnya, then Georgia, plus its leader in the Kremlin was a tired, old and very corrupt former Soviet apparatchik Boris Yeltsin who was soon retire on New Years Eve, 1999. why add on to NATO if its long-feared, Historical oppressor wasnt going to be a potent socio-economic threat for some time to come? By 2004, things were dramatically different but 6-7 years earlier, a very select few in Western intelligence community had that far-sighted expectations or grim assessments.
Remember, this is before Putin and how he viciously and cold-bloodedly changed the nature of the game as the 2000's wore on.