A longer investigation is unlikely to improve their view of the malign influence of the regime of Bashar Assad. It will just give them time to sift between the few unattractive options available to them.

Assad knows that. His policy of playing for time may eventually prove suicidal, as he jettisons all options for peaceful resolution on the way. But meanwhile, his best card is the West’s fear of what might replace him if it did push him out.

This week’s report by Detlev Mehlis, the German prosecutor, came even closer than his last to blaming Syria for the assassination of Rafik Hariri, the former Lebanese Prime Minister, on February 14.

Mehlis delivered it to the 15-member Security Council on Monday, at almost the same time as a car bomb in Beirut killed Gebran Tueni, a prominent publisher and legislator, and one of the fiercest critics of Syria’s influence in Lebanon.

The Security Council will very likely extend the investigation for six months, as Lebanon wants, and as Mehlis recommends — but it must pick a successor to Mehlis who is stepping down. It may also choose to widen the inquiry to take in Tueni’s murder. France said yesterday that it would back that if Lebanon did too, “and we will do our best to have the council going in the same direction”. In Mehlis’s 25-page report, he said that his team had found new evidence implicating Syria in the lorry-bomb murder of Hariri and 22 others in Beirut. He said that there were 19 suspects, whom he did not name, including five Syrian officials questioned by his team in Vienna earlier this month.

His October report implicated the top Syrian security officials, including some very close to Assad and their Lebanese allies, in the killing. This week’s report also says that Syria has been slow in complying with the UN inquiry.

Mehlis said that Syria had burnt some papers and put pressure on one witness to recant. That is controversial because the council adopted a resolution in October threatening Syria with “further actions” — such as sanctions — if it did not fully comply.

John Bolton, the US Ambassador to the UN, said “There’s no ambiguity here. That is no co-operation.” But as he also acknowledges, the council has not decided what to do. It will not find that easy.

If there is a push for sanctions, the council will be split by old allegiances, and also for good reasons. Russia and China would be expected to oppose sanctions. Others will worry that even tighter sanctions will only drive Syria further into the cold and radicalise its people — particularly the young ones, given the soaring birthrate and lack of jobs.

Could other countries do a deal with Syria? The US has tried, several months ago. It offered to take the pressure off in return for Syria cutting off help for the Iraq insurgency, stopping meddling in Lebanon and breaking ties with Hezbollah and Palestinian militant groups.

But it appears to have got a cool response — or at any rate, not a coherent one.

That points to a second problem: working out if Assad — or anyone — is in control of Syria enough to do a deal on its behalf. His intermittent response to the Mehlis report could be a sign of lack of authority — or could be stalling for time.

Assad’s best card is that there is no obvious successor, but alternatives might be worse for the West, with militant Islamic groups moving into a vacuum.

Doing nothing won’t get him anywhere in the long run, and may bring down sanctions on his country. But for now, it is the easy option — and it gives the West a nasty dilemma.

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