He is expected to meet his Belarussian counterpart, Alexander Lukashenko, to sign an accord over the creation of a union between the Slavic neighbours which, while falling short of fusing them into a single state, appears to be a big step towards reintegration.
If it goes ahead, the signing will come after several days of debate in Moscow's political circles about the wisdom of pressing on with reunification with an unreformed and repressive Soviet-style nation whose economic woes could easily turn out to be an extra burden on Russia's crippled exchequer.
After negotiations which saw the head of Russia's Security Council, Ivan Rybkin, fly to Minsk for last-minute talks, Mr Yeltsin's spokesman yesterday announced that the President wanted to proceed. The Union Treaty was a "geopolitical necessity and an economic reality", he said.
But it was unclear how weighty a document the two presidents will sign. The Kremlin said Mr Yeltsin was proposing a shorter one than planned, which would state "in black and white that the parties will transform the Community of Russia and Belarus into a union and transfer some of their powers to the union." But it also said Mr Yeltsin wanted a further month of discussion about a charter outlining the accord.
In doing so, he appears to have bowed to pressure from his own administration, which was deeply split over the issue. The union envisages co-ordinated economic, foreign and defence policies, without giving up national sovereignty. While generally favouring closer ties with Minsk, Boris Nemtsov and Anatoly Chubais - the youthful free-marketeers now calling the shots in the Russian government - reportedly feared it was being rushed through.
Their reservations are shared fivefold by Russian liberals who balk at the idea of closer ties with Mr Lukashenko, whose human-rights record is even worse than Mr Yeltsin's.
Belarussian opposition leaders have been beaten and jailed, demonstrations have been broken up by police using batons and tear gas, and the media have been censored.
Although a closer union of Russia and Belarus may cause frowns in the West - particularly among Russia's big lenders, such as the IMF - it offers domestic advantages to both leaders. Mr Lukashenko, 42, a former Soviet farm director, stands to increase his popularity in his 10 million- strong nation, where he has cultivated a mood of nostalgia for the Soviet Union. Belarussian nationalists fiercely oppose it, but they are a minority.
He may also be covertly eyeing the Russian presidency, although that would require the two countries fully to reunite, a process that will take some years. Such a move would meet with cries of alarm in the West, and particularly in the US, which has been embroiled in a war of words with Mr Lukashenko, culminating in the recent expulsion from Minsk of two US diplomats.
For Mr Yeltsin, there are gains - but also possible losses. It will deepen rifts with ex-Soviet members of the Commonwealth of Independent States, which do not welcome the idea of a Russian super-state. The President of Ukraine, Leonid Kuchma, has said that different levels of unification in the CIS was an "absolute nonsense" and would pave the way to its destruction.
But a Russia-Belarus union would win Mr Yeltsin much-needed applause at home, especially among conservatives and Communists. Many Russians are unconcerned by Mr Lukashenko's murky rights record, and would welcome a move to rebuild part of the Soviet Union and increase Russia's standing on the world stage - especially given Nato's eastward expansion. Moscow would benefit from securing a firmer grasp on a corridor to the West for its oil and gas exports, and by reconnecting businesses that split up when the USSR folded. The treaty is thought to make commerce easier by protecting property rights and - in admittedly loose language - "creating the conditions" for a single currency.
But many warn that Russia's largely privatised economy is currently incompatible with Belarus's centrally planned and mostly state-owned one.
Although Minsk has been claiming growth in output, these figures are thought to be based on stockpiles of unwanted goods. It is, most analysts agree, even worse off than Russia.
Ultimately, the success or failure of today's events depends on whether the union finally comes to fruition. It is worth remembering that a batch of economic agreements signed a year ago by these two men are still widely ignored.Reuse content