Mr Gates said the oil-rich region will remain a central US concern, and that as Mr Obama's pick to stay on the Pentagon he has worked hard to assure that the transition of power goes smoothly.

Mr Gates devoted the main thrust of the speech to Iran and Iraq, and to an appeal to Arab states to embrace the Shiite-led government in Baghdad in order to counter Tehran's influence.

'Anyone who thought that the upcoming months might present opportunities to 'test' the new administration would be sorely mistaken,' he said.

'President Obama and his national security team, myself included, will be ready to defend the interests of the United States, and our friends and allies, the moment he takes office on January 20,' he said.

Mr Gates's speech here comes as the United States is shifting its priorities from Iraq to Afghanistan.

During a brief visit to Afghanistan on Thursday, he promised commanders more troops and resources as the United States draws down its 146,000-strong force from Iraq by the end of 2011.

But the secretary signalled in Manama that he remains concerned about Iraq's long-term stability and Iran's attempts to influence the government in Baghdad.

He said a new status of forces agreement governing the US military presence in Iraq through the end of 2011 marks 'the dawn of a new era in Iraq - where a sovereign, independent and representative government has finally taken root.'

Whether Iraq plays a constructive role in the region depends in part on whether the Arab states act to support the Baghdad government, treating it as an equal and inviting it to take part in regional economic and political forums, Mr Gates said.

'There is no doubt that Iran has been heavily engaged in trying to influence the development and direction of the Iraqi government - and has not been a good neighbour,' he said.

He renewed charges that Iran has been heavily engaged in training and supplying armed militant groups intent on undermining the government.

He said it tested long-range missiles this year that can hit any country in the Middle East, and has 'almost assuredly' geared its nuclear programme to develop nuclear weapons.

Arab states should back financial sanctions called for by the United Nations and 'could be even more influential ... by welcoming the new Iraq into the Arab fold,' he said.

'For other Arabs to withhold support and friendship because of the composition of Iraq's government, or because of past aggressions by a defunct government, would be to increase the risk of the very outcome many in the region fear,' he said.

'Iraq wants to be your partner. And given the challenges in the Gulf, the reality of Iran, you should wish to be theirs,' he said.

Mr Gates praised the Gulf states for making 'significant progress in air and missile defence throughout the Middle East.'

He said all member countries of the Gulf Cooperation Council have expressed interest in or are in the process of acquiring active missile defences and shared early warning on air or missile attacks.

High profile pirate attacks off the coast of Somalia, meanwhile, have highlighted the need for better maritime awareness, he said. -- AFP