Practical Travel Safety Issues - SFO - T1 to T3 - Transit inside "sterile area?

OK, zing me if you want, I did a search and got nada!!

At SFO, can I walk inside the "sterile" area from Terminal 1 (DL) to Terminal 3 (UA)?

Thanks

<edited>The UA SFO airport map (http://www.united.com/page/article/0,6722,1121,00.html) indicates that there is a Star Alliance Bus running from T3 concourse F to IntlT concourse G to T1 concourse B. See the last post in this UA thread:
http://www.flyertalk.com/forum/showthread.php?t=690492