Dick Cheney, the US vice-president, has triggered speculation that he has been using a tour of the Middle East to prepare Iran's neighbours for a possible war with Tehran.
Mr Cheney, whose nine-day tour has included stops in Turkey, the Gulf and Afghanistan, insisted that Iran must not be allowed to develop nuclear weapons.
"The important thing to keep in mind is the objective that we share with many of our friends in the region, and that is that a nuclear-armed Iran would be very destabilising for the entire area," Mr Cheney told ABC News before arriving in Kabul, the Afghan capital, after a visit to Oman.
Challenged on the recent National Intelligence Estimate by US intelligence officials, which concluded that Iran's nuclear weapons programme stopped in late 2003 because of international pressure, Mr Cheney said: "What it says is that they have definitely had in the past a programme to develop a nuclear warhead - that it would appear that they stopped that weaponisation process in 2003.
"We don't know whether or not they've restarted. What we do know is that they had then, and have now, a process by which they're trying to enrich uranium, which is the key obstacle they've got to overcome in order to have a nuclear weapon. They've been working at it for years."
A senior aide to Mr Cheney was forced to deny that the nine-day trip to Turkey and the Middle East was part of a strategy by the vice-president to build support for military action against Iran.
Asked by journalists travelling on Mr Cheney's plane about the vice-president's repeated comments about Iran during his tour, the aide said: "That's not what these discussions are about."
The official acknowledged that Mr Cheney's talks with the Oman government focused on "the concerns we have about the full range of their [Iran's] activities".
These included the country's links to the radical Hamas authorities in Gaza and Washington's belief that Iran has become the dominant power in Lebanon through its sponsorship of Hizbollah.
General Dan McNeill, the US commander of Nato forces in Afghanistan, told The Daily Telegraph in September that advanced weapons smuggled across the Iran border to the Taliban could only have come with the complicity of the Iranian government or elements within its security services.
© 2008 The Telegraph