Colin Powell lashes out at Bush's foreign policy
Mr Powell made his comments on a visit to Ukraine, where he's lecturing university students in the capital Kiev.
“The disagreement that I’ve had with my government over Iran is that we should talk to Iranians, but they’ve chosen a different path, President Bush, Ms Rice, not including me,” he said.
The ex-Bush Secretary of State went on to say that he couldn't rule out a military conflict between the U.S. and Iran.
“I don’t want anyone to think that war between us may break out any time soon but no president, no matter who that president is, will cross out the military option,” Powell said.
Speaking to reporters in Kiev, Mr Powell also called on America to change its tone towards Iraq, the Middle East and Russia. He said it was time to end the seemingly infinite political dispute.
Russia-U.S. relations were of great interest to Mr Powell's audience in Ukraine, a former Soviet state.
General Powell was upbeat in his assessment, saying the Cold War would never repeat itself.
Powell was an advisor to four American presidents but prefers to call himself a soldier.
For 30 years he guarded the Berlin wall against Soviet intrusion.