Gore spoke to reporters in Sydney, where he was promoting the local premiere of his documentary on global warming.
"I haven't completely ruled out running for president again in the future but I don't expect to," Gore said before the Sunday night premiere of "An Inconvenient Truth."
"I offer the explanation not as an effort to be coy or clever. It's just the internal shifting of gears after being in politics almost 30 years. I hate to grind the gears," he added.
Gore, who lost the presidency to President Bush in 2000 in disputed circumstances, said there was no doubt the impact of global warming would be best addressed through the power of the presidency, but making a documentary was second best.
Gore's renewed popularity and movie tours across the United States have spurred speculation of a White House run in 2008. He has previously repeatedly denied such intentions.
The documentary, which Gore narrates, is critical of the United States and Australia for refusing to adopt the Kyoto Protocol for reducing greenhouse gas emissions.
Prime Minister John Howard, a friend and ally of Bush, said he would not meet Gore during his Australian visit and would not heed his advice to sign up to Kyoto.
"I don't take policy advice from films," Howard told reporters.