Russia's ruler Vladimir Putin has demanded that Ukraine adopt a federal constitution. The move is a gambit to gain Moscow more leverage in Ukraine.
Ukraine is diverse, but it is a distinct nation, with a right to independence from Russia; and, despite Russian claims, it does not divide neatly into two sectors.
The west is poorer, heavily dependent on remittances from Ukrainians working abroad, and mostly Ukrainian-speaking: it was not part of the USSR until 1939.
In the middle, Kiev, the capital, and centre of the movement which ousted the corrupt pro-Russian president Yanukovych in February,