* Aliyev accuses BP of "false promises" on oil output
* Could signal third battle line for oil major
* Western firms losing ground to Russians, Kazakhs
(Adds details, background) By Afet Mehdiyeva and Dmitry Zhdannikov
BAKU/LONDON, Oct 11 (Reuters) - Azerbaijan accused BPon Wednesday of making "false promises" on oil output and saidthe state had missed out on $8 billion of potential revenuesfrom what is one of the company's biggest projects in the world.
President Ilham Aliyev said he would take "serious measures"- threatening a third battle front for BP as it seeks asettlement over its Macondo oil spill in the United States andis struggling over the fate of its $25 billion Russian venture.
"Azerbaijan has not received $8.1 billion in revenues,"Aliyev told his government, accusing BP of "grave mistakes" inplanning oil output at the Azeri-Chirag-Guneshli (ACG) fields inthe past few years.
"It is absolutely unacceptable ... Investors who cannotstick to their obligations and contract terms must learnlessons. Serious measures must and will be taken," Aliyev said,according to a text posted on his website.
The comments will also concern BP's partners on the project:Exxon Mobil , Chevron and Statoil whichhave for years watched neighbouring Russia and Kazakhstan takelarger shares in oil projects away from Western companies onaccusations of contract term violations.
Aliyev said the ACG consortium had invested $28.7 billion inAzerbaijan since the 1990s and received revenues of $73 billion.
"Last month BP officially promised to me to fix thesenegative developments as soon as possible ... and moreimportantly, replace people, who made those grave mistakes. Amonth has passed and I don't see those promises beingfulfilled," Aliyev said.
BP's spokeswoman in Azerbaijan, Tamam Bayatly, said thecompany remained devoted to its Azeri operations and would workwith state oil company SOCAR to resolve issues.
BP is the biggest foreign investor in Azerbaijan, where itoperates the 1.2 billion-tonne ACG fields and the giant ShahDeniz gas project, which supplies Turkey.
The prospect of so much non-OPEC crude ensured considerablewestern diplomatic support for the project, a major investmentfor BP.
ACG was supposed to produce more than 1 million barrels perday (bpd) after the project's third phase was completed in 2008.
However, ACG has not lived up to expectations. After hitting823,000 bpd in 2010, output has fallen. Production averaged684,000 bpd in the first half of this year and oil executivesand diplomats told Reuters last month the challenge is now tokeep output at around 700,000 bpd.
(Additional reporting by Margarita Antidze; Editing by RobinPomeroy)
Keywords: AZERBAIJAN OIL/BP