I know there are questions which might sound similar, but this is a complete different one. First I am using the word extending and not expanding and second the question is limited to a time period long before 2008 and even before Putin came to power.
So at the begin of the 90s the Cold War was officially over no Warsaw Pact and even no USSR was there to threaten NATO. The new Russian government was relative pro-western, the most pro-western government in Russia ever. There was no antiwestern propaganda in Russian media, sometimes even the opposite was the case. So no real threat from Russia was expected at that time. It was also clear that extending NATO would change the situation and bring back the confrontation. Some people in Clinton administration have convinced him to wait with extending NATO at least after presidential election in Russia to prevent anti-western candidate from wining. While the arguments against that extension are clear, which ones were for supporting it?