Brussels, July 13 (DPA) Leaders of the G8 industrial countries meeting in St Petersburg, Russia, from Saturday face a tough agenda of global challenges ranging from Iran's nuclear ambitions to North Korea's recent missile launches and the worsening Middle East violence.

The July 15-17 summit, hosted for the first time by Russia which joined the elite club in 1998, will also try to defuse tensions over access to secure energy supplies and revive faltering talks on liberalising world trade.

Leaders from China, India, Brazil, Mexico and South Africa have been invited for a now-traditional "outreach session" on Monday, the last day of the meeting, for talks on combating poverty and boosting global development.

G8 members are Britain, Canada, France, Germany, Italy, Japan, Russia and the United States.

The summit in St Petersburg's luxurious 18th century Konstantin Palace - renovated for a reported $300 million donated by state companies - gives Russian President Vladimir Putin a glittering stage to spotlight Moscow's growing self-confidence as an assertive world player.

But unlike previous G8 summit hosts, Putin can expect tough questioning on the state of Russia's democracy, policies towards former Soviet allies and its conduct as a huge world supplier of oil and gas.

G8 "sherpas" - the experts who organise the summit - have been struggling since early this year to hammer out joint statements on key agenda items including energy security, nuclear proliferation, education and the fight against infectious diseases.

However, the formal declarations look set to be overshadowed by alarm over North Korea's missile tests and Western demands that Iran respond swiftly to an international package of incentives designed to ensure a suspension of its uranium enrichment activities.

Russia has so far resisted calls for threatening tougher sanctions on Tehran.

The recent upsurge of Middle East violence following the standoff between Israel and the new Palestinian government led by Hamas is also expected to dominate discussions.

President Putin wants to keep talks focused on energy security, his key theme for the summit. Few expect the debate to be trouble-free, however.

With oil prices at a record high and China and India emerging as hungry consumers of energy, diversification of oil and gas supplies is the name of the game for all G8 governments - with the exception of Russia which wants to ensure its key role as Europe's supplier.

European Union governments are especially anxious given that Russia provides 25 percent of the 25-nation bloc's gas requirements.

"I think right round Europe and the rest of the world people want diverse sources of energy to give us a balanced energy mix and allow us to make sure that we have energy security in a world of rising prices," British Prime Minister Tony Blair said recently.

Summit participants will be asked to endorse "common principles" to ensure the transparency and openness of world oil markets. But whether these will amount to anything more than a list of good intentions is far from clear.

Moscow has so far refused to ratify the so-called Energy Charter, an international treaty designed to promote market transparency and free energy transit.

European officials make no secret of concerns that Moscow - which briefly cut off gas supplies to Ukraine last January, triggering energy short-falls in western Europe - is not playing by market rules.

European governments are also demanding a reform of Russia's gas sector and say Russian gas giant Gazprom's moves to buy European energy assets must be mirrored by easier reciprocal European access to Russia's still-sheltered state energy sector.

The summit is expected to discuss the future of nuclear power to meet expanding global energy demand.

But G8 members are sharply divided over nuclear power. Italy has closed all its nuclear plants and Germany plans to do so by 2021. In contrast, France produces 78 percent of its electricity from nuclear plants and Paris is planning its next atomic generation. Nuclear revivals are also underway in Britain and the US.

G8 leaders will attempt to revive flagging global trade talks following the recent failure by World Trade Organization members to clinch a deal on liberalising farm trade and curbing costly agriculture subsidies.

In a letter to the summit, World Bank President Paul Wolfowitz warned that "time was running out" for a new anti-protectionist trade deal which could generate $300 billion a year in additional global economic production.