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* Blue-chip FTSE 100 index closes down 0.9 percent
* Royal Mail rebounds on property sale report
* Energy shares down on weaker oil price
* Greek debt jitters hurting market sentiment (Updates with closing prices)
By Liisa Tuhkanen
LONDON, June 12 (Reuters) - Britain's top equity index fellon Friday as lower oil prices hit energy stocks and concernsover Greece's talks with international creditors weighed onsentiment.
The blue-chip FTSE 100 closed 0.9 percent down at6,784.92 points, slightly outperforming major euro zone indexes.
The biggest weight on the index was Royal Dutch Shell, which fell 2.1 percent, trimming nearly 10 points offthe FTSE 100.
Rival oil major BP dropped 2.1 percent and the energy sub-index was down 2.1 percent on cheaper oil.
Oil prices slipped after the world's top crude exporterSaudi Arabia said it was ready to raise output further ifneeded, potentially adding to oversupply.
Royal Mail added 2.8 percent, with tradersattributing the gains to a report indicating Ballymore hasemerged as frontrunner to buy its Nine Elms site in London.
The postal service fell 4.5 percent in the previous sessionafter the British government announced it would sell half of itsremaining stake.
"I don't expect that we're going to see anywhere near themomentum we would have seen when it was privatised initially,but certainly it does seem fairly valued around the 500 pencemark," said London Capital Group analyst Brenda Kelly.
Investors were also focused on Greece's stalled debt talksafter the International Monetary Fund ramped up the stakes onThursday by announcing its delegation had left the negotiationsin Brussels because of differences with Athens.
"Whilst investors have had plenty of time to reduce theirdirect exposure to Greece, any exit of the country from the eurozone will generate questions over the resolve and future of theEuropean Union," Hargreaves Lansdown equity analyst Keith Bowmansaid.
A government official said on Friday that Greece is ready tosubmit counter-proposals to bridge differences with itscreditors and will restart negotiations in Brussels onSaturday.
Athens needs a deal to unlock aid before the end of themonth when it is otherwise set to default on a 1.6 billion euro($1.8 billion) repayment to the IMF. That could trigger capitalcontrols and possibly push Greece out of the euro zone.
Among mid caps, Bwin.Party fell 7 percent aftersaying two of its shareholders had decided to place up to 50million shares in the online gambling firm.
Petra Diamonds dropped 6.9 percent after forecastingfull-year revenue below market expectations.
The miner, which has four producing mines in South Africaand one in Tanzania, had warned in April that full-year resultswould be below market consensus due to variability in grade andproduction mix. (Additional reporting by Atul Prakash; Editing by SusanFenton/Ruth Pitchford)
