UPDATE 2-Bulgaria to push ahead with South Stream

* Bulgaria sees South Stream gas pipeline as beneficial-PM

* PM says roadmap agreement to be signed this week

* To decide on Belene nuclear plant by September

* Bulgaria, Russia to discuss gas supply contracts

(Adds details, background, more comment)

By Tsvetelia Tsolova

SOFIA, July 6 (Reuters) - Bulgaria will push ahead with the Russian-backed South Stream gas pipeline and sign a roadmap agreement for the project after Moscow sweetened its offer, Prime Minister Boiko Borisov said on Tuesday.

Bulgaria and Russia have agreed on ownership of the pipelines on Bulgarian territory and on the usage of existing pipes, Borisov said after talks with Russia's First Deputy Prime Minister Viktor Zubkov.

The centre-right government has been reviewing Russian-backed projects since coming to power last July, saying it needs to check again whether they meet the national interest and European Union agenda. [ID:nLDE6640DD]

Borisov said the 900-kilometer South Stream pipeline, which would pump 63 billion cubic metres of Russian natural gas per year under the Black Sea to Europe from 2015, will be beneficial for the Balkan country, the poorest in the European Union.

"At the moment there are no outstanding issues between Bulgaria and Russia on South Stream. We will sign the roadmap and launch a feasibility study," he told reporters.

Bulgaria has agreed with Russia that Moscow will continue to pump gas to Turkey and Greece through existing pipelines that are owned by Bulgaria, while the new pipes for South Stream, controlled by Russia's Gazprom (GAZP.MM) and Italy's ENI (ENI.MI), will be jointly owned.

Borisov said that Sofia also remains committed to the rival EU-backed Nabucco gas pipeline project, which aims to bring gas from central Asia and Azerbaijan to the EU to diversify gas sources and make the bloc less dependent on Russia.

NUCLEAR DECISION

Borisov said Sofia will wait until September to decide on the fate of the planned Belene nuclear power plant, hoping the government will have a better idea by then of the price of the 2,000 megawatt plant, its financing and investor interest.

"By September the first reactor will be ready and then we will have to decide whether to pay for it or start legal actions and pay penalties," he told reporters.

The government has put Belene, for which the previous administration has contracted Russia's Atomstroyexport, on hold, saying Bulgaria needs to reconsider the benefits of the project, which has an estimated cost of more than 6 billion euros ($8.05 billion).

Cash-strapped Bulgaria has said it does not plan to provide state or corporate guarantees for Belene and would push ahead only with involvement of a strategic European investor.

Sofia would likely abandon another Russian-backed project -- an oil pipeline aimed at carrying Urals crude to Greece -- due to environmental concerns and strong opposition by residents of Burgas, where the link is planned to start.

Zubkov said Moscow was ready to give it up if an international environment assessment, which has already been commissioned, shows the pipeline endangers the environment. He said he did not expect environmental hurdles.

Russia will also look at options to lower gas prices for Bulgaria at pending talks for new supply contracts, but said Sofia has first to explain why the price for consumers is much higher than the one Gazprom charges, Zubkov said.

Borisov said he his government still has to investigate why the prices rise so much for end-consumers.

Russia sells gas at an average price of $339 per 1,000 cubic metres to Bulgaria, while Bulgarian businesses and households pay between $500-$576, Zubkov said.

"These are very high prices," he said. (Editing by Sam Cage and Alison Birrane) ($1=.7453 Euro)