You caused me to research. It has not actually been denied: https://www.stopfake.org/en/feigned-bismarck-citation-about-separating-ukraine-from-russia/

Also, these quotes by Bismarck really are interesting: https://www.azquotes.com/author/1426-Otto_von_Bismarck

• The secret of politics? Make a good treaty with Russia.
• What we learn from History is that no one learns from History.
• Never believe anything in politics until it has been officially denied.
• The division of the United States into federations of equal force was decided long before the Civil War by the high financial powers of Europe. These bankers were afraid that the United States, if they remained in one block and as one nation, would attain economic and financial independence, which would upset their financial domination over the world. The voice of the Rothschilds prevailed... Therefore they sent their emissaries into the field to exploit the question of slavery and to open an abyss between the two sections of the Union.