MOSCOW (BBC) -- Russian President Vladimir Putin has voiced optimism that negotiations with the World Trade Organization (WTO) over membership may be finalized next month.

Putin said Russia could sign the protocol before the G8 meeting of the world's eight most industrialized nations in St Petersburg in July. Russia's attempts at WTO membership have stalled, amid accusations that it is being judged too harshly by the U.S.

The U.S. is the only member of the WTO not to have approved Russia's entry. -------Established practice

The U.S. has questioned Russia's human rights record, its control of key energy resources, enforcement of intellectual property rights, and restrictions on foreign companies doing business there.

"Unfortunately, the position of the American negotiators changes often and they return to questions that we thought had been solved earlier," Putin said on Wednesday.

"This does not correspond to established practice," he complained.

Russia has been waiting for a decade to join the WTO.

Moscow has become increasingly frustrated by the lack of progress made regarding membership and last month said that U.S. firms may lose business if the delays and problems were not resolved.

Also on Friday, Russia's statistical office said the economy grew by 5.5% in the first three months of 2006 compared with a year earlier.

Russia's gross domestic product (GDP) expanded by 6.4% in 2005, and 7.2% in 2004.