The government reacted with predictable speed after Kirsan Ilyumzhinov, the flamboyant president of Kalmykia, a semi-autonomous republic on the north shores of the Caspian, declared on television that he might seek "associate" membership of the 89-region federation. Associate membership appears to mean having significantly greater independence, whileremaining formally within Russian borders.
The spectre of the federation's break-up is a sensitive issue for the Kremlin, which ordered troops into Chechnya in 1994 in a vain effort to keep it under Moscow's control.
Yesterday Moscow showed every sign of taking Mr Ilyumzhinov's rumblings seriously. Kalmykia has part of the shoreline of the strategically important Caspian Sea, which it would be loath to lose.
Critically, Mr Ilyumzhinov's threats came with an announcement that Kalmykia will not be contributing any more tax to Moscow's coffers - a sum estimated at $200m - as it was no longer getting funds from the federal budget.
Gennady Seleznyov, speaker of the lower house, described Kalmykia's threats as "no joke", amid calls from parliament for federal prosecutors to investigate the republic's finances.
The National Security Council, which will convene to discuss the issue in the next few days, said in a statement yesterday it would make recommendations to Mr Yeltsin on concrete measures "to ensure the unconditional observation of the Russian constitution".