Creating the customs union proved to be more complicated than anticipated and the three countries have postponed its planned launch date.
The European Union says Russia, which remains the largest economy still outside the 153-member body, could join the WTO within a year amid generally better ties with Brussels and Washington.
But as talks have been going on for the past 16 years, experts are far from certain about the final outcome.
The following are potential scenarios on how Russia's long-standing bid to join the WTO may play out.
Russia speeds up WTO Talks, Dumps Customs Union For Now
Russia is looking to diversify its exports away from commodities and energy and shift trade from slow-growing developed markets to fast-expanding emerging and frontier markets. WTO membership will help Russia achieve both goals, increase the country's attractiveness to foreign investors and facilitate new bilateral trade deals.
"Many countries which are looking into trade with Russia would like it to become a WTO member before launching bilateral trade initiatives," said Yaroslav Lissovolik, Chief Economist at Deutsche Bank.
Remaining obstacles include the status of Russian state-owned enterprises, intellectual property rights and farming subsidies.
The WTO bid is likely to dominate a Russia-EU summit next week and a potential summit between Presidents Dmitry Medvedev and Barack Obama later this year.
Russia Goes For Customs Union if WTO Chances Unclear
The move would upset foreign investors, who were already rattled when Prime Minister Vladimir Putin gave the order last year to suspend talks with the WTO until the creation of the customs union with Belarus and Kazakhstan.
Analysts struggled to explain Putin's move, which came at a time when Russia was closer to joining the WTO than ever. Some saw in it frustration at the slow pace of talks, or Moscow's unwillingness to open its markets at the peak of the global economic crisis.
"You change the rules of the game overnight and tell everyone about it at the last minute. Russia still has a lot of explaining to do," said one Moscow-based European investor.
Russia will have to compromise on thorny issues such as duty-free oil exports -- a demand of Belarus -- or car import duties which help protect the Russian auto industry from foreign second-hand vehicles.
Belarus wants to import Russian oil duty-free, process it at its own refineries and export oil products at a hefty profit.
Russia, which ships 1 million barrels per day of oil to Europe via Belarus, says it will only cover Belarus' domestic consumption with duty-free oil supplies.
The issue looks set to dominate a summit of the leaders of Russia, Kazakhstan and Belarus on July 5.
Russia Creates Union With Kazakhstan Only
Russia may try to create a customs union with Kazakhstan only, Russian government sources have said -- although Putin's spokesman Dmitry Peskov said this would be the "least desirable" outcome.
The economies of Russia and Kazakhstan have similar profiles and both focus on energy, which partly explains the lack of big differences in negotiations. The move would complicate talks with the WTO and create only marginal economic benefits.
It would further worsen relations between the Kremlin and Belarussian leader Alexander Lukashenko, who has recently opposed integration with Russia amid better ties with the West and due to what analysts say are his fears of losing control of Belarus.
It could also increase the likelihood of oil pricing spats between Moscow and Minsk which have previously led to disruption of Russian oil flows across Belarus to Germany and Poland.
Closer Ukraine Ties
The Kremlin has invited Ukraine to join the customs union but Kiev says the idea contradicts its WTO commitments.
Ukraine, already a WTO member, is a la
