CRAWFORD - The US rationale for war in Iraq has morphed from ousting strongman Saddam Hussein, to countering Al-Qaeda militants to its latest incarnation -- facing down what officials in President George W. Bush's administration call the Iranian "threat".
"Iraq is the convergence point for two of the greatest threats to America in this new century: Al-Qaeda and Iran," Bush said last week, renewing accusations that the Islamic republic is backing Iraqi militias hostile to US forces and covertly seeking nuclear weapons.
"If we succeed in Iraq after all that Al-Qaeda and Iran have invested there, it would be a historic blow to the global terrorist movement and a severe setback for Iran," he said.
With Saddam dead and Al-Qaeda weakened -- according to Bush -- Iranian-financed extremists, which top US commander in Iraq David Petraeus has called "special groups," have emerged as a key reason for maintaining US troop levels in Iraq.
"Unchecked, the 'special groups' pose the greatest long-term threat to the viability of a democratic Iraq," Petraeus said last week as he told US lawmakers of military strategy in Iraq for the coming months.
However, exactly what steps the United States may take to counter this "threat" remain unclear, and depend largely on Bush's decisions in his remaining nine months in the White House.
Bush told ABC News that he had no intention of attacking Iran, but vowed to protect US interests and refused to rule out the use of force altogether.
"The message to the Iranians is: we will bring you to justice if you continue to try to infiltrate, send your agents or send surrogates to bring harm to our troops and/or the Iraqi citizens," Bush said.
Asked to elaborate on this "justice," Bush replied: "It means capture or kill, is what that means."
Bush repeated that "all options need to be on the table, but my first effort is to solve this issue diplomatically," and added that he was amused by unfounded rumors of an impending attack.
"I'm chuckling, because, you know, from my perch, my perspective, these rumors happen all the time ... I wouldn't say they're amusing. It's part of the job, I guess."
Defense Secretary Robert Gates on Sunday confirmed US concern with Iranian actions but said the chances of the United States "stumbling" into a confrontation with Iran through skirmishes in Iraq "are very low."
"We are concerned about their activities in the south. We are concerned about the weapons that they are sending in -- that they continue to send in to Iraq," Gates told CBS.
The defense secretary noted that a recent government offensive against Shiite militias in the southern Iraqi city of Basra had revealed "the level of Iranian malign influence in the south and on their economic heart line through Basra."
In London, The Independent newspaper reported Monday that the United States and Iran have been conducting secret back-channel discussions on Tehran's nuclear program and frozen relations between the two countries.
The paper quoted former US under secretary of state Thomas Pickering as saying that a group of former US diplomats and foreign policy experts had been meeting with Iranian academics and policy advisers "in a lot of different places, although not in the US or Iran" for the past five years.
Still, speculation has been rife over a potential US conflict with Iran, which is pressing on with its nuclear activities despite three sets of UN sanctions over Iran's failure to heed repeated ultimatums to suspend uranium enrichment.
US ambassador to Iraq Ryan Crocker has framed Iranian activities in Iraq as a "proxy war" with the Americans, even as administration officials have hailed the retreat of Al-Qaeda due to increasing involvement by Sunni tribal chiefs.
Crocker on Friday foresaw a similar reaction in Iraq, saying that Iran's support for militias fighting the Iraqi government may cause a Shiite "backlash."
Yet the Bush administration has launched "an inter-agency assessment of what is known about Iranian activities and intentions, how to combat them and how to capitalize on them," the Washington Post reported Saturday.
Brookings Institution expert Suzanne Maloney said that "disastrous Bush policies fostered a sectarian Iraq that has helped empower Iranian hardliners.
"Rather than serving as an anchor for a new era of stability and American pre-eminence in the Persian Gulf, the new Iraq represents a strategic black hole, bleeding Washington of military resources and political influence while extending Iran's primacy among its neighbors."
© 2008 Agence France Presse