* OPEC secretary general post comes up in 2013
* Saudi, Iran, Iraq, Ecuador compete for the job
* Four candidates nominated, panel may convene in Oct
* Group has struggled to agree in the past
By Alex Lawler and Amena Bakr
LONDON/DUBAI, Aug 16 (Reuters) - OPEC has delayed a meeting of officials to help select its new secretary general, delegates from the oil producers' group said, putting off delicate talks that could reignite rivalry for influence as Saudi Arabia, Iran and Iraq seek the top post.
A panel of officials was initially planned to convene at the Vienna headquarters of the Organization of the Petroleum Exporting Countries during August, but the meeting is now more likely to take place in October, officials said.
OPEC has often struggled to agree on a secretary general and the task of appointing a successor to the outgoing Abdullah al-Badri comes as Western sanctions on Iran have heightened political tensions within the 12-member group.
Without a decision on the post before December, OPEC could start 2013 without a permanent figurehead, potentially adding to its difficulties in managing the oil market should predictions of a slowdown in global oil demand prove to be correct.
Four of OPEC's 12 members have put forward potential successors to Badri, a Libyan whose term finishes at the end of 2012.
The panel, consisting mainly of OPEC governors - oil officials who represent their countries on the group's board of governors - will review the candidates and consider how the organization should proceed, officials said.
"There are some options to have a meeting but we have not agreed yet," an OPEC delegate, who like other officials declined to be identified, said. "It was in August but then changed to October. It has not been finalised."
Several delegates said the August talks were delayed because of difficulty in fixing the meeting around participants' schedules. But one said the group was reluctant to tackle the succession at present.
"OPEC doesn't want to deal with this delicate issue at this time and would rather delay it," the delegate said.
Any decision on Badri's successor will be made by OPEC's oil ministers, who are next scheduled to meet in December.
The secretary general is the main representative on the world stage of the producer group, helps formulate its output policy and is in charge of OPEC's Vienna secretariat.
Saudi Arabia nominated its OPEC governor, Majid Al-Moneef, for the role, officials said in January. It was followed by Iraq, which proposed Thamir Ghadhban, energy adviser to Iraq's prime minister. Iran nominated a former oil minister, Gholam Hossein Nozari, and Ecuador also put a candidate forward.
The talks arise as Western sanctions on Iran over Tehran's nuclear work have led to a drop in Iranian output and heightened political tensions. Iran has criticised Saudi Arabia and its Gulf Arab allies for pumping more oil to keep a lid on prices.
OPEC did not select a replacement for Badri when its oil ministers last met, in June, and inter-Gulf political rivalry hampered a deal last time the post was up for grabs.
Badri's appointment, starting in 2007, ended a three-year impasse over the job, during which OPEC rotated the secretary general post around member countries for short terms of one year.
The post has tended to go to officials from smaller OPEC producers to spread influence beyond top producer Saudi Arabia and Iran, OPEC's traditional No. 2 whose output has now been overtaken by Iraq as sanctions curb Iran's oil sales.
OPEC officials have also raised the possibility of Badri being asked to remain in the post beyond the end of his term if a successor cannot be chosen. That would mean OPEC waiving its own rule that the secretary general serve no more than two three-year terms.