"We're very excited by an endorsement of such a respected and influential organization, " Hattaway said.

CNN: Sierra Club endorses Gore for president

Gore spokesman Doug Hattaway said he has yet to review the proposal, but could not rule it out.

CNN: Gore adviser proposes global environmental watchdog

"(Gore) certainly wants to work at a national and international scale, " Hattaway said.

CNN: Gore adviser proposes global environmental watchdog