The United States has done itself no favours by the way it has handled its revelations about Syria’s purported covert nuclear weapons programme. It was always going to be vulnerable to charges that it had cried wolf once, in Iraq, only to find its intelligence lethally wrong. But in making claims about Syria’s secret efforts to build a bomb with North Korean help, it has asked the world to take too much on faith and left itself open to every charge of bending intelligence to fit the politics.

The accusations have been simmering for weeks – and in a low-key way, for seven months, since Israel bombed a Syrian site without much explanation. But they were brought into the open on Monday evening by Michael Hayden, the CIA Director, who said that the alleged Syrian reactor destroyed by the Israeli raid would have produced enough plutonium for one or two bombs within a year of becoming operational.

The US must be braced for critics to say that they have heard this kind of thing before. It is not just the American and British assertions about Iraq’s weapons of mass destruction. But the continuing struggle to persuade Iran to drop its nuclear ambitions produces a steady fountain of such prophesies: how many years until it can make enriched uranium, how many more until it gets a bomb, how many more bombs per year. And so on.

No surprise that the US has been criticised by the International Atomic Energy Agency, the UN nuclear watchdog, for failing to disclose the information earlier. The relationship between the two is hardly neutral, as the IAEA, under its Director-General Mohamed ElBaradei, has challenged the American approach to the Iranian problem and has appeared more accommodating of Tehran’s explanations. But the IAEA is on solid ground this time: one of its jobs is to try to detect the illicit use of nuclear material, and it cannot do that if its members withhold intelligence vital to that work.

A senior official told reporters last week that the US had kept the intelligence back because it had come from Israel and the US did not want to provoke a Syrian counter-attack. But this is ridiculous: the Israeli attack was ample cause for retaliation, were Syria to feel in need of one.

The second flank of attack has come from Republicans in Congress, uninhibited in criticising President Bush in the run-up to the November elections. Pete Hoekstra, the top Republican on the House of Representatives intelligence committee, said that officials had presented Congress last week with “compelling information”. But he said that they should not have waited seven months. He added that congressional anger might jeopardise support for the US’s attempts to reach a breakthrough deal with North Korea about curbing its own nuclear work. And he argued, plausibly, that keeping secret the details of North Korea’s alleged help to Syria may have hindered these talks. Bush may still have slender hopes that he might add a deal to his legacy, out of a dwindling list of possibilities.

At a time when interest in civil nuclear power is growing – and should, to help to stave off climate change – there are bound to be more alarms about the diversion of the technology to military goals. The US will play an essential part in trying to curb proliferation as nuclear power spreads. But it cannot expect to be believed if this is how it sounds the alarm.

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