Ukraine’s supporters of Western integration hope to draw a million people to a protest against the authorities’ decision to spurn a historic EU agreement and seek closer ties with old master Russia.

The ex-Soviet nation of 46 million has been lurching through its worst political crisis since the 2004 pro-democracy Orange Revolution as it once again debates its exact role as a geopolitical bridge between Russia and western states.

President Viktor Yanukovych’s abrupt U-turn last month on a deal with Brussels that could have pulled Kiev out of Moscow’s orbit has exposed deep cultural fissures that have been running between Ukraine’s nationalist west and more Russified east for most of its post-Soviet history.

Opposition leaders – openly backed, to Russia’s dismay, by top US and EU officials – are demanding the government’s immediate dismissal and snap elections that could break Yanukovych’s dominance over politics.

Both conditions have been rejected by despite signs that some in the government are willing to open direct talks.

The Kremlin has also accused the West of aggressively interfering in the international affairs of a sovereign nation that has chosen to remain on good terms with Moscow.

EU governments have hit back at Russia with charges of using threats of potential trade sanctions against Ukraine as a form of blackmail that would assure Kiev’s continued reliance on Moscow.

The size of Sunday’s protest threatens to eclipse earlier rallies in Kiev and western Ukraine that brought several hundred thousand out on the streets on December 1.

Those demonstrations were fed in part by anger over a violent police crackdown the day before on a few hundred protesters who were occupying Kiev’s icon Independence Square – the heart of the 2004 revolt.

But now the opposition is outraged at news that Yanukovych had paid a snap visit to Russia for talks with President Vladimir Putin about a new strategic partnership that could indefinitely delay talk of an EU pact.