Vladimir Putin will travel to China next week to cement long-standing ties with the world's top energy consumer, the prime minister's first trip abroad since he announced his planned Kremlin comeback.

Accompanied by a 160-member delegation including top tycoons, Putin will visit Beijing on October 11-12 for energy and political talks with Chinese Prime Minister Wen Jiabao and President Hu Jintao.

Putin has paid frequent visits to China in his capacity as president and prime minister since he took power in 1999.

His latest visit to Beijing follows his last month's announcement that he plans to reclaim the presidency in a bid that may keep him in power until 2024.

While the timing of the working trip appears to be a coincidence, observers say it is richly symbolic and could see Putin lay out his foreign policy priorities for years to come.

"It's symbolic that Putin, who's very well known in China, is going there at this particular time," Sergei Sanakoyev, head of the Russian-Chinese Centre of Trade and Economic Cooperation, a Moscow-based lobby group, told AFP.

Russia, the world's largest energy producer, and China, the world's largest energy consumer, set much store by their bilateral ties.

China became Russia's top trading partner for the first time last year and the two countries seek to nearly double trade to $100 billion by 2015 and then to $200 billion by 2020.

Moscow and Beijing are both veto-wielding permanent members of the UN Security Council and this week infuriated the West by blocking a UN resolution against Syrian President Bashar al-Assad's deadly crackdown on protests.

Putin's expected return to the presidency will likely give a further boost to bilateral ties.

"The Chinese have betted on him returning to the Kremlin. It's an open secret," Sanakoyev said.

Chinese businessmen and politicians, he said, have always known that Putin remains the top figure in the Russian political pecking order even after he installed his protege Dmitry Medvedev in the Kremlin in 2008.

The powerful prime minister, who will seek a third Kremlin mandate in March presidential polls, this week talked up ties with China at an investor conference, his first major public address since the September 24 announcement.

"We have a huge common border with China. We have lived together for thousands of years," he said. "Today our bilateral ties are perhaps at their highest level in history aside from a very brief Soviet postwar period."

The leaders will oversee the signing of a series of agreements, a Putin spokesman said, declining further details. Plans to pump Russian gas to China over the next three decades are expected to top the agenda.

Russian gas giant Gazprom and China National Petroleum Company signed a framework agreement in 2009 that could eventually see almost 70 billion cubic metres of Russian gas sent to China annually for the next 30 years.

A firm gas contract has so far proved elusive as talks have become mired in pricing disagreements. Contrary to expectations, Hu's June visit to Moscow delivered no breakthrough.

Chinese officials said last November the prices backed by the two sides differed by $100 per 1,000 cubic metres. Sanakoyev, citing his own information, said the two sides are believed to have narrowed the difference to $50.

A Gazprom spokesman declined comment, saying the talks were confidential.

Valery Nesterov, an energy analyst at Troika Dialog investment bank, was dubious that Putin would clinch a firm contract with China because Gazprom's negotiating position is weakened by intensifying competition and other factors.

"It is difficult to expect a breakthrough taking into consideration the complicated, long-drawn-out talks and the fact that the deadline has been pushed back many times," he said.

In an eyebrow-raising incident, Russia's security service the FSB revealed this week that it had been holding a Chinese national identified as Tong Shengyong for the past year on espionage charges linked to Russia's S-300 surface-to-air missiles.

Neither the Kremlin nor Beijing, a major purchaser of Russian weapons, issued any comment in a possible attempt to suppress the issue ahead of the talks.