BERLIN - King Salman of Saudi Arabia has cancelled attendance at this week's G20 summit in Hamburg, the German government said Monday, as Riyadh is engaged in a diplomatic standoff with Qatar.

It is a crisis almost a year in the making. The pot began simmering last January with the ascension to the throne of King Salman bin Abdulaziz. Since then, one explosive ingredient after another has been added into the mix.