By Dmitry Zhdannikov
LONDON, Aug 30 (Reuters) - Iraqi state oil firm SOMO hasblacklisted three tankers involved in shipping crude fromKurdistan, stepping up pressure on the semi-autonomous regionamid tense talks on sharing oil revenue.
Kurdistan has been exporting crude independently via Turkeysince mid-2015 after saying Baghdad had failed to respect an oilrevenue-sharing deal and transfer enough money to Erbil.
Baghdad, which exports most of its oil from the Gulf, hassaid Erbil was not exporting enough crude under the deal.
Last week SOMO sent market participants a letter - seen byReuters - saying it would no longer allow the ships MaranCentaurus, Four Smile and SN Olivia, which had been shippingKurdish oil, to enter Iraqi ports or export its crude.
Baghdad has regularly sent such letters in the past. It hadrefrained from doing so in recent months as it was preparing fornew talks on revenue-sharing with Kurdistan and had resumedshipping crude from the northern Kirkuk fields to Kurdistan.
SOMO did not immediately respond to a request for comment onthe latest letter.
The semi-autonomous region exports around 500,000 barrelsper day (bpd) of its own crude from the Turkish Mediterraneanport of Ceyhan. Baghdad's shipments to Kurdistan of Kirkukcrude, which it restarted earlier this month, have been onlyhalf the previously supplied 180,000 bpd.
Baghdad said last week it could divert the Kirkuk crude toIran by truck instead of sending it to Kurdistan via pipeline ifthe talks on revenue-sharing broke down.
The move may further undermine Kurdistan, whose funds havebeen sapped by its fight against Islamic State militants. Theregion's oil exports do not cover its budget needs.
Diverting oil to Iran could also damage the unity of IraqiKurdistan, which had been counting on additional crude fromKirkuk.
The only way SOMO could truck oil to Iran would be throughthe central Kurdish region of Suleimaniya, controlled by thePatriotic Union of Kurdistan, a rival of the KurdistanDemocratic Party of Kurdish President Masoud Barzani in Erbil.
"The move could be very divisive for the Kurds but also itcould set a precedent for other political parties in Iraq todemand their own oil," a government source in Erbil said.
Sending crude to Iran would also involve significantlyhigher trucking costs - estimated at up to $20 per barrel - thansending oil by pipeline to the Mediterranean, thus furtherreducing revenues from oil exports. (Reporting by Dmitry Zhdannikov; Editing by Dale Hudson)