The crash of Ukraine International Airlines Flight 752 over Iran, which killed all 176 people on board, is a tragedy. The human cost should not be obscured by the recriminations that have followed. Many families in Iran, Canada, Britain and elsewhere have suffered a devastating blow. In addition to the lives lost, countless more lives have been irreparably damaged.

The Iranian government’s admission of responsibility is welcome. It should have come sooner. Tehran’s hasty claim, within hours of the disaster, that mechanical problems were to blame provoked immediate suspicion. Within 24 hours, video and other evidence emerged, clearly indicating the airliner was hit by a ground-to-air missile, yet Iranian spokesmen and diplomats persisted with their implausible denials.

The otherwise commendable decision by Hassan Rouhani, Iran’s president, to express “deep regrets” for a “disastrous mistake” attributable to what he called human error is thus tainted by the delay in doing so and by a sense that Iran ultimately had no choice. Its initial instinct was to attempt a cover-up, but it was not working. International investigators were on their way. The electronic evidence was damning. Iranian culpability could not be hidden.

The consequences of this tragedy may be far-reaching, not least for the domestic credibility and standing of the regime. In the short term, the exact circumstances must be established. Why was the Ukrainian plane allowed to take off only hours after Iran attacked US military bases in Iraq and was nervously anticipating a violent US response? How did military commanders fail to distinguish between the radar signatures of a large passenger airliner and an enemy missile?

These and other catastrophic shortcomings suggest a startling lack of military and technical proficiency on the part of the Islamic Revolutionary Guards Corps, from whose base outside Tehran the fatal missile was launched. Few in Iran have hitherto dared to challenge the IRGC, which enjoys the patronage of the supreme leader, Ayatollah Ali Khamenei, has large financial and commercial interests and operates independently of the armed forces and foreign ministry.

General Qassem Suleimani, whose assassination by the US triggered this latest crisis, was the powerful leader of the IRGC’s elite al-Quds force. His killing united the country behind the regime in a vast outpouring of grief and anger. That rare moment of unity now appears to have shattered. Khamenei has publicly ordered an unprecedented investigation into IRGC actions. Severe punishment awaits those involved. Meanwhile, Iranians took to social media to express fury, shame – and a too-familiar sense of betrayal over the official lies they were fed.

The IRGC’s aura of invincibility and Iran’s reputation for military skill, recently burnished by the Iraq attacks, have been damaged. That in turn has domestic consequences for an unpopular regime recently attacked by street protesters infuriated by food and medicine shortages, unaffordable fuel prices and pervasive governmental incompetence, corruption and cronyism.

Iran has overreached, strategically, militarily and politically

For the anti-regime protesters, many of whom were shot down and killed by the IRGC in November, lack of accountability at the top is normal. Iran’s leadership has belatedly come clean with the world over Flight 752. Now it faces a reckoning with the Iranian people.

If the regime’s unusual admission of fallibility brings a new openness and greater candour about its many other failings, that at least would be a positive development at a moment of great sadness. If the tragedy, coupled with Suleimani’s death, leads to a re-evaluation of the IRGC’s disruptive, often aggressive operations in Iraq, Syria, Lebanon and elsewhere, then that, too, will be widely welcomed.

In many respects, Iran has overreached, strategically, militarily and politically. It is suffering enormous human and economic stress. This might be a good moment to pause and reconsider what it is trying to achieve.

The US would be well advised to encourage any such Iranian re-evaluation, rather than attempt to exploit the tragedy to advance its war of attrition. Unfortunately, that’s not the style of arch-hawks such as Mike Pompeo, the US secretary of state who has emerged as Donald Trump’s most influential adviser. Pompeo, who has presidential ambitions, seems to be on a sort of personal evangelical mission to destroy Tehran’s clerical-led regime, whatever the cost in innocent lives.

Trump and his sidekick should back off – and show some respect for the dead. Mohammad Javad Zarif, Iran’s foreign minister, tempered Rouhani’s apology by suggesting the tragedy was the result of “US adventurism”. This defence, which will certainly be repeated in the coming days, confuses the issue. Iran shot down the plane. The blame is Iran’s, fairly and squarely. And Iran has accepted it – unlike the US in 1988 after its missiles brought down Iran Air Flight 655 over the Gulf, killing 290 people.

Yet it is also true that the US has unnecessarily, provocatively and irresponsibly escalated its confrontation with Iran to a point of such extreme tension and fear that accidents were likely to happen, as we warned here last week. US policy undoubtedly helped create the febrile conditions in which this disaster occurred. Like Iran’s leaders, Trump should examine his conscience and think again.