Iran's standing in the Middle East has been bolstered by President George W Bush's "war on terror" and its power will continue to grow unless stability is restored to its neighbours, a top think tank said.
Royal Institute for International Affairs report
London's Royal Institute for International Affairs said wars in Iraq and Afghanistan and Israel's conflict with the Palestinians and with Lebanon's Hizbullah had put Iran "in a position of considerable strength".
"There is little doubt that Iran has been the chief beneficiary of the war on terror in the Middle East," the RIIA said in a report on the region.
"The United States, with coalition support, has eliminated two of Iran's regional rival governments -- the Taliban in Afghanistan in November 2001 and Saddam Hussein's regime in Iraq in April 2003 -- but has failed to replace either with coherent and stable political structures."
Seeing a regional political void opening, Iran had moved swiftly to fill it, the report said, and now has a level of influence which cannot be ignored.
The report said Tehran sees Iraq as its "own backyard" and had now superseded the US as the most influential power there, affording it a "key role in Iraq's future".
"Iran is also a prominent presence in its other war-torn neighbour with close social ties -- Afghanistan," it added.
The RIIA warned the US that Iran's new-found influence would make it far more difficult to confront Tehran. The West needed to understand better Iran's links with its neighbours to see "why Iran feels able to resist Western pressure", it added.
Western countries, led by the United States, are locked in a bitter dispute with Iran over its nuclear programme.
Iran, the world's fourth largest oil exporter, says it will not give up what it says is its right to peaceful nuclear technology. The West suspects Tehran is seeking nuclear weapons.
The RIIA report said Iran would continue to "prevaricate" in the nuclear dispute, confident in its position.
"Iran is simply too important -- for political, economic, cultural, religions and military reasons -- to be treated lightly," the report said.
"The US-driven agenda for confronting Iran is severely compromised by the confident ease with which Iran sits in its region."