Serbia is not a close NATO supporter but it is completely surrounded by NATO countries. Therefore it cannot afford to resist the policies of the US unless it wants to be bombed again. Milocevich was the last leader to resist 'Westernisation'. The Serbian population is definitely not against Russia, but its politicians are now pro-western.. as far as I know anyway.. but maybe I'm wrong? Do you have links to any articles which would show the current Serbian government as anti-western?
You say Serbia supports the idea of joining the EU, but if that happens it will also be indirectly integrated with NATO since most EU members are also in NATO.
Serbia (1,200): Surrounded by NATO (wiki);
potential EU candidate (link)
These were the only factors which I used to determine Serbia's position. It is possible that I made a mistake because I haven't spent much time researching Serbia's politics, so maybe you can help me..