If all other arguments fail, blame the Jews. That was the message this week from Egypt's top religious figure, the Sheikh of Al-Azhar.

Declaring the Islamic State "criminals", he justified attacks against them because they are part of a "Zionist plot" to undermine "Arab unity".

The Western media conveniently chose to ignore this idiocy.

But that it came from the head of the most revered institution in Sunni Islam, whose salary is paid by the Egyptian government, tells us that we should indeed pay close attention.

This is the first time since the outbreak of the Syrian civil war that any Arab regime has played the Israel card.

Until now, the Sunni Arab states, like the Islamic State, had resorted mainly to anti-Shia bigotry to rally their masses, with a Qatar-based Sunni cleric even calling for genocide against them. However, the hatred did not resonate amongst most ordinary Sunni Arabs.

Millions of Egyptians did not travel to Syria, for example, to join the jihad after deposed Islamist President Morsi urged them to; and Sunni Saudis have not massacred their fellow Shia.

Now that Shia-dominated Iran has taken the fight to Islamic State, effectively creating a Shia buffer between the jihadists and the Gulf, there is little more political mileage in that track.

With the Sunni Arab regimes terrified of possible Islamic State-inspired revolts at home, it is back to Jewish conspiracies and Israel bashing.

The West, too, is resorting to the tried and tested, backing these dictatorial Sunni Arab regimes while coordinating militarily with their (and their own) arch-rival, Iran, inside Iraq.

If there is any method in all of this madness, it is now very difficult indeed to see - even more so after Washington this week agreed to create an all-new Syrian rebel force to fight both the Assad regime and the Islamic State.

Even if - combined with a relatively stable Iraqi government and US-led air-strikes - this latest harebrained scheme comes off, it will likely leave Israel in an even more precarious spot.

For with the Islamic State now tarred with the "Zionist agents" brush, when it finds itself on the ropes it may decide to hit out at Israel in a last, desperate effort to divide the Arab masses and their regimes, and the latter and the US.

John R Bradley is a journalist and author