Rupert Cornwell: If you can't talk publicly, talk in secret

What is the scariest building in Washington? For me, the answer is, as Vice-President Dick Cheney likes to say of water-boarding, a "no-brainer". Not the Pentagon or even the DC holding jail, but an empty building on Massachusetts Avenue with an oriental motif on the front and a half-hidden blue-tiled dome at the back, just down the road from the magnificent Lutyens mansion where the British ambassador lives. The building is scary not for what's there - but for what isn't there.

Alert readers will have already guessed. I am talking about what used to be the Iranian embassy, until diplomatic relations were severed in the wake of the 1979 hostage crisis in Tehran. The past few days here have been utterly dominated by the mess in Iraq - timetable or no timetable, more troops or fewer troops, "stay the course" or "cut and run". Obscured by the anguish over the Iraq crisis is the grim fact that we are heading for an even worse one with Iran.

Yesterday, the Iranians announced they had taken another step in the uranium enrichment programme that the West believes is intended for the production of nuclear weapons. At the same time, Washington is stepping up pressure for sanctions on Tehran at the United Nations. Every sign is that this game of chicken will continue, until President Bush declares at a certain point that "diplomacy has run its course". We all know what that particular phrase meant in the context of Iraq. Yet this time, the stakes are even higher.

The US can't invade Iran as it did Iraq. But it can bomb its nuclear sites, destroying them and doubtless much else besides. For all their belligerent talk, Iran's rulers cannot want this to happen. But they would surely respond to such an act of war by closing the Straits of Hormuz, making Iraq even more ungovernable than it is today, and generally stirring up more trouble across the Middle East, tipping the entire region into chaos. And yet, as that empty building on Massachusetts Avenue reminds, the two main actors in this drama aren't even talking to each other.

Diplomatic relations should be a practical matter, reflecting the realities of life, not a gift that can be bestowed or withdrawn as a sign of approval or disapproval. Governments often do not like each other, but they must deal with each other, even at arm's length. The US and the Soviet Union from time to time expelled each other's diplomats - but never did they entirely break off relations.

Sadly, the Bush administration doesn't take that view with Tehran. And maybe there is simply too much baggage for normal relations: the CIA-mounted coup of 1953 that restored the Shah, the 444-day US embassy hostage crisis in Tehran, the "war on terror". But if the front door at 3005 Massachusetts Avenue must stay shut, what about the back door?

If ever there was a case for back-channel diplomacy, it is now. For either the US or Iran to give ground in public would be seen as a sign of weakness. The great virtue of the back-channel is precisely that because no one knows it exists, no one loses face.

Curiously, there has been no greater and more enterprising exponent of back-channel diplomacy than the US. The ultimate master of the technique was the devious and manipulative Henry Kissinger, who as Nixon's national security adviser set up his own private channel with the Soviet Union, through Moscow's ambassador Anatoly Dobrynin, entirely bypassing the State Department. The arrangement was humiliating for William Rogers, the titular Secretary of State. But it did allow the two countries to hold rational discussions on the burning issues of the day, even as they were exchanging fierce criticism in public.

The back-channel gambit to end them all was, of course, Kissinger's secret trip to China in the summer of 1971, during a visit to Pakistan during which he absented himself for two days, officially struck down by a stomach bug. Instead he and three aides flew to China. A quarter of a century later, one of those aides, Winston Lord, recounted to me some of the hilarious details of the subterfuge - how Kissinger forgot his shirts and had to borrow one that said on the back "Made in Taiwan", and how when the plane landed, he elbowed aside his colleagues in his determination to become the first US official to set foot on Chinese soil since the Communists took power in 1949.

In retrospect, that trip initiated one of the great geo-strategic turning points of the age, a new working relationship between the Soviet Union's two great rivals that shifted the balance of influence away from Moscow. It took place at the very moment China was publicly railing at the US for its "imperialist" involvement in Vietnam. Why not something of the same, albeit at a less exalted level, with Iran now?

No one is asking Condoleezza Rice - whose public outreach to the likes of Syria and Iran is confined to phrases such as: "They know what they've got to do" - to don the veil, get on a secret flight to Tehran and personally negotiate a deal between the Great Satan and a founder member of the Axis of Evil. But there are other ways.

And the tide here may be shifting. One thoughtful Republican senator, Chuck Hagel of Nebraska, has long urged the White House to open talks with Iran. And James Baker, the former secretary of state, who heads the bipartisan Iraq Study Group, declares that "it is not appeasement to talk to your enemies". What matters with negotiations is not where (or how) they start, but where they end up.

The stakes could not be higher. Iran and the US have a vast amount to talk about: Iraq, Tehran's nuclear programme, economic aid, terrorism. In the end, the choice is surely between some form of grand bargain, or war. So why not a bit of exploratory back-channel work, in which each side can talk honestly, without pre-conditions? Yes the Iranians may decide to blow the back channel. But its very existence would show the Americans had been serious about negotiating, something which is not apparent today. Of course, despite everything, a back channel may be already be up and running now. That is the joy of back channels. But I doubt it.