"We want Russian accession to the WTO and will continue negotiating," Bush said after bilateral talks with Russian President Vladimir Putin, ahead of a full Group of Eight summit later in the day.

He said a deal, which would end Russia's 13-year campaign to join the World Trade Organization, was "almost reached" but added that "there's more work to be done."

Appearing with Bush at a press conference after their meeting, Putin said that although "our personal relations help us work together ... they also don't stop us from defending our national interests in any sphere."

"It's a complex process that lasts years. I can't say that we were not expecting such a complication. We will continue to work, defending our interests and the interests of our growing economy."

Russian chief negotiator Maxim Medvedkov earlier told Interfax news agency that "the protocol will be signed neither today nor within the coming weeks."

But his US counterpart, Trade Representative Susan Schwab, was more optimstic, saying the parties had made "a lot of progress" and that reaching consensus was "a question of weeks."

As part of its accession bid, Russia has already signed bilateral agreements with its other key trading partners and now needs a green light from the United States to join the 149-member Geneva-based WTO, which sets global rules.

Russia is today the only major power operating outside WTO trade regulations, and US officials have said repeatedly they would prefer to have Moscow formally bound by the organization's rules.

For Russia and Putin, agreement on WTO membership here would have constituted a major summit success while serving to confirm Russia's rising stature as a global commercial and economic powerhouse.

Putin earlier this month warned that Russia would no longer feel obliged to respect WTO regulations in principle if it were denied official membership.

Russian press reports Saturday said the main stumbling block was Washington's insistence on an easing in Russian health regulations, which some of its trading partners suspect are applied in order to justify politically motivated embargos.

But the United States has also been pressing for Russian guarantees on the opening of the country's financial sector to foreign participants and for a reduction in agricultural subsidies.

Prospects for a deal appeared to brighten earlier in the week when Russian Finance Minister Alexei Kudrin said negotiators had cleared a key obstacle, with Washington dropping a demand that Russia allow foreign banks to open their own branches - rather than legally-registered Russian subsidiaries - on its territory.

In exchange Russia would lower barriers to foreign participation in the insurance sector.

Bush on Saturday also hinted at domestic, political hurdles that need to be overcome in the United States before an agreement can be signed with Moscow.

"We want the agreement to be reached to be accepted by the United States Congress," the president said.

At present Bush enjoys "fast track" trade negotiating authority, which means that Congress can either approve or reject - but not amend - trade deals negotiated by the White House. But his fast track mandate is scheduled to end in the middle of 2007.

For Russia to enjoy normal trade relations with the United States, Bush will have to win Congressional backing for the abrogation of the Jackson-Vanik amendment, which could prove to be complicated.

The amendment, approved in 1974 in response to actions by certain countries that denied Jews the right to emigrate to Israel, imposes limitations on US commercial relations with Russia.