Washington: The United States appears headed on a collision course with Iran that could lead to a war with 'disastrous" consequences, a former adviser to ex-president Jimmy Carter has warned.

"We think we are going to avoid war by moving towards compulsion," Zbignew Brzezinksi, who was national security adviser to Carter in the late 1970s, told an audience at an Atlantic Council think tank event in Washington on Tuesday.

"But the more you lean towards compulsion, the more the choice becomes war if it doesn't work. That narrows our options in a very dramatic way," said the former official, who remains an influential voice on US foreign policy.

Brzezinksi said he was concerned about an escalation in "rhetoric," as the US approach to Iran's nuclear program appeared solely focused on forcing Tehran to comply with international demands, leaving Washington little flexibility.

"A lot of small decisions are being made which in the meantime narrow your freedom of choice in the future," he said.

Tuesday’s gathering featured four former national security advisers, including president Richard Nixon's powerful deputy Henry Kissinger.

Brzezinksi warned repeatedly of his concerns that the United States could stumble into a war with Iran.
"If we slide into a conflict with Iran, in this or that fashion, the consequences for us will be disastrous, disastrous on a massive scale and also globally at the same time," he said.

Brzezinski was in office in 1979 when America's ally, the Shah of Iran, fell from power in a revolution that resulted in an Islamic theocracy in Tehran.

After the seizure of the US embassy in Iran and the taking of American hostages that same year, Brzezinski presided over a plan to rescue the captives but the military operation failed before it got off the ground.

Tensions have steadily grown between Iran and the United States in recent months as Washington has pushed for stricter sanctions to punish Tehran over its nuclear activities and amid speculation Israel may be weighing possible pre-emptive military action.