(Adds statement from NOC in Tripoli)

By Ayman al-Warfalli

BENGHAZI, Libya, Aug 29 (Reuters) - A state oil firm loyal to Libya's official government based in the east of the country has postponed a conference in Dubai to discuss oil majors' existing contracts with the OPEC member country.

The conference is a fresh attempt by Libya's internationally recognised government to control state oil firm NOC, which is at the centre of a conflict between two rival administrations four years after the ousting of leader Muammar Gaddafi.

The event will now be held on Sept. 16, two weeks later than originally planned, the organisers said in a statement late on Friday.

"We have been requested by many clients and companies to postpone the event by two more weeks to allow their senior managers to attend," the statement said.

The eastern government, which lost the capital Tripoli a year ago to a rival administration, has set up new management for NOC, based in the city of Benghazi, but oil buyers still deal only with the established state firm NOC in Tripoli, which has processed oil sales for decades.

In a separate statement, NOC in Tripoli, in an apparent reference to the conference invitation, said that only statements posted on its website were reflecting the views of the state oil firm. It did not elaborate.

The eastern NOC entity had said in its original invitation it wanted to "discuss legally signed agreements and contracts" with foreign oil buyers and service firms in Dubai.

The conference will take place three months after NOC in Tripoli held a similar event in London to show it was in charge of Libya's oil reserves and to reassure customers that the political conflict would not affect the state oil firm.

The eastern government said in March it wanted oil buyers to pay through a new bank account in Dubai to replace a decades-old payment systems via NOC in Tripoli.

But oil customers have refused to sign any deal with the eastern entity due to legal concerns as geological data to prove ownership of oil reserves is stored at NOC in Tripoli.

Libya's conflict has reduced output to less than 400,000 barrels a day, a quarter of Libya's production before an uprising toppled Gaddafi.

The United Nations has urged the warring parties not to touch the state oil firm or the central bank, which processes oil revenues, Libya's lifeline.

(Reporting by Ayman al-Warfalli; Writing by Ulf Laessing; Editing by Alison Williams) ((ulf.laessing@thomsonreuters.com; follow me on twitter @ulflaessing; Reuters Messaging: ulf.laessing.reuters.com@reuters.net))

Keywords: LIBYA OIL/