Russia's proposal for joining the World Trade Organisation (WTO) as part of a customs union with Kazakhstan and Belarus is "unworkable", US Secretary of Commerce Gary Locke said yesterday.

"According to most members of the WTO (Russia's proposal) is just unworkable, unprecedented and would only delay matters," Locke told reporters.

"The United States wants greater clarification with respect to the statements by Prime Minister Vladimir Putin."

Putin baffled the WTO last month by announcing that Moscow would alter its accession bid and seek membership as a single customs bloc with two of its ex-Soviet neighbours, Kazakhstan and Belarus.

Locke expressed surprise over Moscow's move, saying that prior to Putin's announcement Washington had been "on the cusp" of an agreement with Russia on its accession by the end of the year.

"The bottom line is that the United State and Russia were on the cusp of reaching an agreement about accession to the WTO," he said. "Russia in our view was very close to fulfilling various requirements at least from our side.

"This came as a bit of a surprise to us."

He added, however, that the United States was still supportive of Russia's long-delayed efforts to join the trading bloc. "We're still very hopeful and very eager and very supportive of Russia's WTO accession."

Locke was in Moscow travelling with US President Barack Obama.

In meetings with Russian ministers this week, Locke said, Moscow's proposal had been described to him as a "parallel track" entry plan by which all three ex-Soviet states would continue their accession negotiations independently but in consultation with one another.

All three countries have ongoing talks with the WTO. Some observers have speculated that Russia's move is specifically aimed at delaying its entry to the free trade bloc amid broader resentment of Western-led institutions.

Russian Finance Minister Alexei Kudrin said last month that Russia would seek entry only once its customs bloc with Belarus and Kazakhstan is in place from 2011.

Russia is the largest world economy still outside the WTO, and the delays in accession talks had recently been marked by growing expressions of Russian impatience.

Putin's shock announcement stumped trade negotiators and again halted the already tortuous 15-year process for Moscow to join the WTO on its own.

Initial talks on its accession began in 1993 but have been repeatedly delayed by disputes over a variety of issues, including Russia's war with Georgia last year.