MANAMA, Bahrain - Persian Gulf countries must demand that Iran come clean about its past nuclear ambitions and openly vow to not develop such weapons in the future, U.S. Defence Secretary Robert Gates said Saturday.

In a broad call to diplomatic arms, Gates exhorted leaders from the Gulf to band together to force Iran to stop its uranium enrichment program and to help the fragile Iraqi government.

"Everywhere you turn, it is the policy of Iran to foment instability and chaos, no matter the strategic value or cost in the blood of innocents - Christians, Jews and Muslims alike," Gates said in a keynote address at an international security conference.

"There can be little doubt that their destabilizing foreign policies are a threat to the interests of the United States, to the interests of every country in the Middle East, and to the interests of all countries within the range of the ballistic missiles Iran is developing," he continued.

He goaded Iran to acknowledge its bad behaviour - from arming terrorists in Iraq to its support for militant organizations like Hezbollah and Hamas.

Some questioners challenged his thinking on Iran, underscoring the divide among Arab nations over America's tough stance on Tehran. Asked if the United States would be willing to talk with Iran, Gates said the behaviour of Iran's new leadership "has not given one confidence that a dialogue would be productive."

Noting that Iran embraced the recent U.S. intelligence estimate that concluded it had actually stopped atomic weapons development in 2003, Gates drew chuckles from the crowd when he suggested Iran should accept that all other intelligence conclusions about its conduct are true.

Earlier this week, Iranian President Mahmoud Ahmadinejad hailed the document as a "declaration of victory" for his country.

"In reality, you cannot pick and choose only the conclusions you like of this National Intelligence Estimate," Gates said.

"Since that government now acknowledges the quality of American intelligence assessments, I assume that it also will embrace as valid American intelligence assessments of its funding and training of militia groups in Iraq."

Gates said Iran should also acknowledge it delivers weapons to terrorists in Iraq and Afghanistan, supports terror groups and continues to develop ballistic missiles that could be used to carry weapons of mass destruction.

His rebukes didn't reach any Iranian ears directly, since Iran abruptly decided not to attend the gathering, organized by the London-based International Institute for Strategic Studies.

The U.S. defence secretary, who was in Iraq earlier in the week, also called for Gulf nations to cast aside their sectarian differences and support Iraq's struggling new government.

He told the gathering the decline in violence is due to new military tactics, the improved Iraqi military, the decision by some militants to reject terrorism and the "groundswell of ordinary citizens who have risen up to fight against al-Qaida."

Nations in the Middle East, he said, have the most to lose if Iraq dissolves in chaos, and the most to gain if it becomes a stable, secure trading partner.

Gates' stop in Bahrain is the last stop on a frenetic, weeklong tour of the region, which included meetings with military commanders on the battlefields in Iraq and Afghanistan.