The U.S. remains the only country out of the 58-member Working Party on Russia's accession with which Moscow has yet to sign a bilateral protocol.
Josette Shiner said the two sides would continue the negotiations and attempt to overcome the existing differences.
Russia's Economic Development and Trade Minister German Gref and United States Trade Representative Susan Schwab will continue negotiations Friday on Russia's accession to the World Trade Organization in St. Petersburg, an insider source said.
During negotiations on Wednesday and Thursday, Russia made a concession and agreed to let U.S. insurance companies enter its market, after lengthy debates.
"We have agreed to the opening of foreign insurance companies' branches, but have insisted that no branches of foreign banks will be opened in Russia," Finance Minister Alexei Kudrin said Thursday.
The issue of access to Russia's financial services market has been the main stumbling block in Russia's bilateral negotiations with the U.S. on its WTO bid.
The U.S. had previously insisted that its banks be granted permission to open branches in Russia, but Moscow rejected the idea, saying the Russian banking system was too weak to withstand foreign competition.
Gref said this week that talks with the U.S. could be completed before the Group of Eight summit opens Saturday in St. Petersburg. Finance Minister Alexei Kudrin said Thursday that the sides would sign a bilateral WTO deal on Friday or Saturday.
Gref and Schwab are discussing a number of issues that have so far stalled the negotiation process. These include intellectual property rights, import duties and agricultural subsidies.
U.S. President George W. Bush - who said Monday he was "optimistic" that a deal could soon be clinched - is due to arrive in St. Petersburg Friday for a meeting with Russian leader Vladimir Putin on the eve of Russia's debut G8 summit.
If a bilateral deal with the U.S. is signed, a working report on Russia's accession to the WTO will have to be drafted, which may take another few months, Kudrin said.
