Monday, April 12, 1999 Published at 15:52 GMT 16:52 UK
Analysis: How strong is the Slavic union?
Yugoslav Federal Parliament deputies vote to join the Slavic union
By BBC regional reporter Tom de Waal
The idea of Yugoslavia signing up to the union treaty between Russia and Belarus was first proposed last year by nationalist radicals from all three countries.
But the Russian Foreign Ministry, amongst others, quietly dismissed the idea as both impractical and against Russia's interests.
It was revived again by the Communist speaker of the State Duma, Gennady Seleznyov, who visited Belgrade last week.
It is a measure of how opinion towards the West has changed since the Nato bombings began that the Russian Foreign Minister Igor Ivanov said in response that his ministry would "study" the possibility of Yugoslavia joining the union.
That was a much warmer response than before.
Rhetoric or reality?
However, the vote has everything to do with nationalist rhetoric and not a lot with reality.
To try to include distant Yugoslavia with its devastated economy, seems fantastic to say the least.
The treaty of economic union signed by the Russian and Belarussian presidents in May 1996, during Mr Yeltsin's re-election campaign has so far yielded few results.
Its main achievement, a customs agreement, has suffered since Russian customs officials complained that the Belarussian frontier was too open to smuggling and Russia was losing revenues.
Last December the two countries declared that they wanted to deepen their integration and work towards full currency union and legal harmonisation - ideas which need to be confirmed in a referendum later this year.
Economists and international lenders like the IMF are very sceptical about closer unions.
The Belarussian economy is still almost exclusively controlled by the state, there is almost no foreign investment and the currency is weak.
These are all problems which are even more acute in Yugoslavia.
Official response crucial
On an issue where symbolism is all-important, the official response in Moscow to the vote will be watched very closely in the West.
Belarus and Yugoslavia are the two most authoritarian and anti-Western states in Europe.
If Mr Yeltsin and his government say they want to show more solidarity with them, it will mark a further toughening of Moscow's position.