* Putin is 60 on Sunday, plans quiet celebrations
* He faces protests but opposition is divided
* Economy's dependence on oil price is a key threat
Russian President Vladimir Putin turns 60 on Sunday, his grip on power weaker than in the past but under little immediate threat if the oil price stays high.
Adoring supporters will celebrate in cities from Siberia to Rostov-on-Don in southern Russia, where the ruling party's loyal Young Guard will unfurl a banner on a bridge which they say symbolises Putin's role by uniting Asia and Europe.
Opponents will make their feelings known much closer to home, protesting near Moscow's Red Square under the banner: "We're sending the old man into retirement".
The organisers plan to send their own symbolic message by asking protesters to bring gifts suitable for a pensioner - anything, perhaps, from reading glasses to a pipe.
The man himself will be relaxing with his close family and plans no special celebrations, Kremlin spokesman Dmitry Peskov said. Just a few months into a third term as president, he may be reaching retirement age, but has no plans to retire.
After 12 years as Russia's paramount leader, opinion polls show Putin enjoys higher ratings than most Western politicians, but they are down from their peak during the oil-fuelled economic boom of his first presidency from 2000 until 2008.
In August the independent Levada polling group said 48 percent of Russians had a positive view of him compared to 60 percent in May when he began a new six-year term.
But a poll published this week showed one in five Russian women would still be happy to marry him, even though he is about to reach an age at which he can collect his pension.
"Age doesn't matter in what Vladimir Putin does or does not do," said Konstantin von Eggert, a political commentator, adding that Putin's views had changed little since he came to power.
"His vision is rather pragmatic and reduces a person to two functions - he can either be a friend or a foe."
WHO WILL SUCCEED HIM?
The foes are now more obvious than before. Putin has faced the biggest protests of his rule in the past year, and foreign investors and the Russian opposition alike point to a lack of clarity in his economic and political policies.
He has responded to the protests by pushing through laws which the opposition says are intended to stifle dissent - including tightening legislation on defamation and increasing fines for protesters.
"When a person is in power he changes drastically, especially if he wants to rule forever," said Boris Nemtsov, an opposition leader, looking back on the years since Putin succeeded President Boris Yeltsin.
"Putin who cut taxes, Putin who tried to continue Yeltsin's politics, and the current angry, greedy, thievish, corrupted, authoritarian leader - they seem to be two different people."
The Kremlin has dismissed such accusations and Putin still has many fans. There will be a concert on Sunday on his hometown, St Petersburg, and supporters have applied for a permit to hold a 60,000-strong march and rally.
State-run television channels will celebrate his years in office with what are expected to be glowing profiles.
Putin has cultivated an image as a strong leader never shy of criticising the West, embraced the resurgent Russian Orthodox Church and used Russia's oil revenues to dampen discontent. Populist policies include generous increases in public sector pay, extra social benefits and regional development programmes.
But his macho image, built over the years with stunts such as shooting a tiger with a tranquiliser dart and flying a fighter jet, has increasingly become an object of satire.
Among the many fawning words written about Putin in the Russian press this week, a few articles have also appeared asking questions about the lack of an obvious successor or a transparent succession process.
"In Russia, Putin now stands alone at the summit of a mountain with steep slopes which no climber can get a grip on," the popular Moskovsky Komsomolets daily wrote on Friday.
"In theory we have a mechanism for a change of power. In practice we do not have one."
BATTLE BEHIND THE SCENES?
Dmitry Medvedev, the protégé who stood in as president for four years because the constitution barred Putin from seeking a third successive term in 2008, appears out of favour.
Medvedev is now prime minister but the two have taken a gentle dig at each other in recent weeks, and Putin has started undoing some of the more liberal policies Medvedev introduced.
This has, in turn, reignited debate about rivalries between the powerful interest groups around Putin and Medvedev.
But some analysts believe that while disagreement between Putin and Medvedev may exist, there is no real rupture in their relationship and their occasional political back and forth is meant to give the appearance of plurality under Putin.
"You should never forget how loyal he is to the people he's worked with," said an experienced Western executive in Moscow.
If all goes well for Putin, he can seek another six-year term when his mandate runs out in 2018. This would keep him in power longer than Leonid Brezhnev, whose 18-year rule in Soviet times is often criticised for economic and political stagnation.
Economists and political analysts say the greatest immediate threat to Putin is not the opposition, which remains divided, but the Russian economy's dependence on energy exports.
The oil price at which Russia's budget balances is above $100 per barrel, making the economy - and Putin - vulnerable to any fall to a price that is considerably lower.
"The government is popular (with ordinary Russians) because it spends more and more and more," said Sergei Guriev, Rector of the New Economic School in Moscow
But he added: "If the oil price were $55, and the government could spend only what it can afford at $55, I think Putin would be gone."