* Areva-Siemens consortium is building Olkiluoto 3 for TVO
* TVO says new start date "hard to accept"
* Areva blames delayed approvals
* Areva, Siemens see no additional financial hit (Adds Siemens statement, shares)
HELSINKI, Sept 1 (Reuters) - Areva-Siemens, the consortium building Finland's biggest nuclear reactor, said on Monday the start date of the much delayed project will be pushed back to late 2018 - almost a decade later than originally planned.
Areva-Siemens blamed disagreements with its client Teollisuuden Voima (TVO) over the plant's automation system, the latest blow for a project that has been hit by repeated delays, soaring costs and disputes.
Olkiluoto 3, which will be Finland's fifth and biggest nuclear reactor as it aims to increase energy self-sufficiency, was originally due to start operating as early as 2009, but has been hit by repeated delays and soaring costs.
Areva said construction, which started in 2005, would not be completed before mid-2016, and that operations at the 1,600 mega-watt plant were not expected to start until late 2018.
TVO, whose owners include Finnish paper companies UPM and Stora Enso as well as utility Fortum , said the late start-up was hard to accept given that much of the project was complete to a high technical standard.
"The delays are because the planning of the plant has taken needlessly long," Jouni Silvennoinen, TVO's project head, told Reuters on Monday.
"We haven't examined the supplier's detailed schedules yet, but our preliminary view is that we could do better (than 2018)."
Areva said it had faced difficulties getting the reactor's systems approved, and urged TVO to take a more active role in the project.
Silvennoinen said he welcomed all initiatives to speed up construction.
The delayed project is also postponing another nuclear plant plan at the site in western Finland. TVO has a general permit to build Olkiluoto 4, but it recently asked the government for a five-year extension to that licence.
Finland plans to raise its total nuclear reactor fleet to seven in the 2020's.
TVO and Areva have traded accusations about who is to blame for delays and extra costs, and the International Chamber of Commerce's (ICC) arbitration court is processing a dispute on cost overruns between the consortium and TVO.
Areva-Siemens last year raised its compensation claim to 2.7 billion euros, while TVO has submitted a counter claim of 1.8 billion euros.
The plant's construction costs were initially estimated at around 3.2 billion euros. TVO has not updated the sum, but many say it could double at least.
Siemens, which has a 27 percent share of the consortium, meanwhile put the blame on Areva, saying its part of the contract - the non-nuclear, or Conventional Island, part of the power plant - was virtually complete.
"Siemens is currently performing the first commissioning and testing phase in the Conventional Island," it said on Monday, adding that joint commissioning and testing would begin once Areva had finished its share of the work, the so-called Nuclear Island.
Siemens said it did not expect to book further financial charges due to the project, after 152 million euros ($200 million) in 2012 and 87 million in the year before, as its risk provision already took uncertainties in the schedule into account.
Areva also said the updated schedule would not have an impact on its project losses, which totalled 3.9 billion euros as of end-June.
Shares in Areva were up 0.2 percent by 1053 GMT, outperforming a 0.2 percent decline by French blue-chips , and Siemens was up 0.06 percent.
Finnish-Russian consortium Fennovoima is also having difficulties proceeding with its project to build a new plant in western Finland because the Ukraine crisis is driving away investors. ($1 = 0.7614 euro) (Additional reporting by Maria Sheahan; Editing by Mark Potter and Susan Thomas)