With Russia sending warships to discourage foreign intervention in Syria, and China drawn more deeply into Iran's confrontation with the West, great power politics is swiftly returning to the Middle East.

After Russia pulled back from the region at the end of the Cold War, the United States and its Western allies faced few external rivals in attempts to influence events. But as the US withdraws from Iraq, emerging economic powers reshape the globe and are themselves sucked ever deeper into the Gulf by their energy needs, that era seems over.

What we are seeing is the U.S. losing its ability to shape events in the region, even though it remains by far the pre-eminent military power, says Waleed Hazbun, director of the Centre for Arab and Middle Eastern Studies at the American University in Beirut.

You're seeing others moving in to fill the gap.

In some ways, experts say, there are echoes of 19th and 20th century scrambles for resources, territory and influence.

Bottom line: there will be more players in the sandbox, says Hayat Alvi, lecturer in Middle Eastern studies at the US Naval War College. The Middle East has always been the venue for the Great Game... Rising powers will see opportunities and advantages in engaging in (that), just like the colonial powers.

Whereas Moscow and Beijing remained largely on the diplomatic sidelines for the 1991 and 2003 Iraq wars and even last year's Libya campaign, they increasingly demand their voices are heard.

Both have signalled a clear intention to prevent any regime change intervention in Syria; but Russia's deployment of its flagship aircraft carrier and escorts to Syria's port of Tarsus this month drew a starker than usual line in the sand.

Whilst some Russian officials talked down the importance of the visit, saying it was preplanned, others said it was intended as a signal. The warships have since moved on, however, and as violence continues to escalate, Moscow is finding itself under ever greater pressure to abandon its one-time ally.

Meanwhile, the success of U.S. and EU sanctions against Iran will be almost entirely dependent on the extent to which China joins -- with growing signs Beijing views Tehran as a useful tool to divert US military force from Southeast Asia. India, too, looks reluctant to play along with the wider western strategy of attempting to strangle Tehran economically to push it from its nuclear program and is also seen as a rising regional player.

There are stark differences to the colonial era, however.

Outside players must contend with increasingly assertive local powers, particularly Turkey, Saudi Arabia and Iran itself, keen to fill the gap left by a U.S. pullback. To make matters more complex, the Arab Spring overturned long-held assumptions of stability and the control governments can exert on events.

Things are becoming less manageable as the region degenerates into deepening socio-economic malaise, says Asher Susser, professor of Middle Eastern politics at Tel Aviv University, Local trends are forcing external powers to pay attention and not vice versa.

GLOBAL PRIORITIES

Nevertheless, the more muscular regional approach of Moscow and Beijing in particular appears already increasingly tied to their wider global agendas.

Russia's support for Syria's Bashar al-Assad is seen largely as a move to defend its Cold War-era foothold in the country as well as block the road to future Libya-style intervention. With presidential elections due later this year, Prime Minister Vladimir Putin is seen keen to show himself facing down the West and making his mark beyond Russia's borders.

With both Moscow and Beijing facing an uptick in protest on their own territory in the last year, neither has any desire to watch another autocratic leader dragged from office. If the Kremlin allows passage of an Arab League proposal to the U.N. Security Council for Assad to yield power, it will do so only with great reservations and provision excluding military force.

With its own colossal energy reserves, Moscow has little need to keep the region's energy states on side. China's dependence on Middle Eastern oil and gas, however, is expected to rise further in the years to come, perhaps drawing Beijing ever deeper into its conflicts and politics whether it wants to be or not.

If the United States succeeds in its ambition to become more energy self-sufficient with new technology and greater domestic resource exploitation and pulls back from the region, some believe China could even become the pre-eminent external power in the Middle East -- perhaps in a growing rivalry with India, also pulled in by its energy needs.

In the shorter term, there are clear signs the face-off over Iran's nuclear program may also be tied into a wider growing geopolitical rivalry with the West. With Beijing increasingly concerned over the buildup of U.S. forces in its immediate neighbourhood, some voices argue Iran plays a useful role in keeping US forces deployed elsewhere.

The US strategic adjustment highlights the importance of Iran to China, said an editorial in China's English-language Communist Party-published Global Times on January 6 after Washington unveiled its new Asia-facing defence strategy. Iran's existence and its stance form a strong check against the U.S. China should not treat Iran following US cultural, social and political values.

Chinese officials might be willing to use sanctions to negotiate better oil prices from Iran, but there seems relatively little prospect that they will stop buying even if Tehran's rival Saudi Arabia makes up the difference in output.

Each time the West tightens the leash, Beijing quietly avails itself of the slack, says Thomas Barnett, a former strategist for the U.S. Navy and now chief analyst at political risk consultancy Wikstrat. The more explicitly Washington bases its global strategic military posture on the perceived Chinese threat, the more Beijing will welcome - and even overtly encourage - these diversions.

REGION TIRED OF US DOMINANCE?

In Washington, Tel Aviv and elsewhere, there are openly discussed worries a more assertive China and Russia could prove drivers of instability, extending a lifeline to regimes the West would rather see isolated and weakened.

For Israel in particular -- long a beneficiary of U.S. power in the region and already somewhat struggling to manage relationships with a more assertive Turkey and post-revolution Egypt less influenced by Washington -- that could prove an awkward dynamic.

Moscow and Beijing, however, say their aim is simply to secure peace and avoid conflict -- particularly important to a China desperate to maintain the flow of Gulf oil and avoid the kind of global economic shock a regional war would produce.

The West's actions in Iraq in particular, officials from both powers argue, did little to improve regional stability. A pre-emptive war in the Gulf, they say, could ultimately prove just as dangerous as a nuclear armed Iran.

With the Arab Spring in part a rejection of a US policy of backing autocratic client states, some even in the US believe such arguments could play well amongst Middle East populations.

The regional public is tired of the same superpower exerting its will on the region, says Alvi at the US Naval War College. They might just set out the welcome mat to the Chinese.

But others say it is far too soon to write off the United States, at least as long as its military remains by far the most potent force in the area and the primary guarantor of security for many of its states.

The entire issue of American decline -- globally and in the Middle East particularly -- is overblown and exaggerated, said Robert Satloff, executive director of the Washington Institute for Near East Policy. The day I see Middle Easterners lining up outside the Chinese embassy for visas, sending their kids to Chinese universities or preferring that Chinese aircraft carriers -- and drones and missile defence systems etc -- protect their territory and assets, then we can have a serious discussion about decline.

(Reporting By Peter Apps)