Linux – Changing default system locale on CentOS 5

I'm running a CentOS 5 server and the current default locale seems to be always set as:

LANG=zh_CN.GB18030
LC_CTYPE="zh_CN.GB18030"
LC_NUMERIC="zh_CN.GB18030"
LC_TIME="zh_CN.GB18030"
LC_COLLATE="zh_CN.GB18030"
LC_MONETARY="zh_CN.GB18030"
LC_MESSAGES="zh_CN.GB18030"
LC_PAPER="zh_CN.GB18030"
LC_NAME="zh_CN.GB18030"
LC_ADDRESS="zh_CN.GB18030"
LC_TELEPHONE="zh_CN.GB18030"
LC_MEASUREMENT="zh_CN.GB18030"
LC_IDENTIFICATION="zh_CN.GB18030"
LC_ALL=zh_CN.GB18030

When I run

export LC_ALL=en_US.UTF-8
export LANG=en_US.UTF-8

Things seem to work fine until I restart my system or relogin; it returns to Chinese again. I checked my /etc/sysconfig/i18n config and it reads:

LANG="en_US.UTF-8"
SYSFONT="latarcyrheb-sun16"

Cant's seem to figure out other ways to set the default system locale. I don't want to do it in .bashrc or .bash_profile because I want it to be globally set for the system. What to do?