On 25 July 1914, Laszlo Count Szogyeny, the Austro-Hungarian Ambassador to Germany (pictured), sent a coded private telegram to Leopold Count Berchtold, the Austro-Hungarian Minister of Foreign Affairs. In his telegram, Szogyeny informs Berchtold of a conversation between the German Minister of Foreign Affairs and the Italian Ambassador to Germany concerning Austro-Hungarian policy towards Serbia.
Count Szogyeny to Count Berchtold. Berlin, 25 July 1914.
The German Foreign Minister [Gottlieb von Jagow] told me today that the Italian Ambassador [to Germany] was wondering why your Excellency had not given his government — an allied Power — information of our step in Belgrade [i.e. the Austro-Hungarian ultimatum to Serbia] sooner.
Herr Jagow answered that Germany had not either been informed any sooner, and that he considered this quite correct, because the conflict, which is now beginning, was an exclusive affair between Austria-Hungary and Servia.
This answer was then telegraphed to the German Ambassador in Rome, so that he should know what language to hold, but he will be instructed in addition to say to [the Italian Minister of Foreign Affairs the] Marquis San Giuliano, that Italy did not previously inform its allies of the ultimatum of 24 hours to Turkey.
Source: 1919 Austro-Hungarian Red Book, with minor edits.