* Spain promises to build EU energy ties with Russia
* Gazprom signs supply deal with Gas Natural
* Medvedev says door still open to LUKOIL-Repsol deal
* Iberdrola, Inter Rao to study joint projects
(Updates with details on Gas Natural, Gazprom accord)
By Oleg Shchedrov and Ben Harding
MADRID, March 3 (Reuters) - Russia and Spain signed an energy agreement on Tuesday that will give Spanish companies greater access to Russian fields and could smooth the path for Russian firms to buy stakes in Spanish energy companies.
The framework deal which was unveiled at a joint press conference between Spanish Prime Minister Jose Luis Rodriguez Zapatero and Russian President Dmitry Medvedev covers the development of oil and natural gas as well as its transport and sale, including liquefied natural gas (LNG).
Zapatero was keen to point out the agreement also included renewable energy, where several Spanish companies hold major positions including wind turbine maker Gamesa, and Iberdrola, the world's largest wind energy producer.
"(This agreement) opens the door to collaboration between our country and one of the biggest energy players in the world," Zapatero told a news conference in Madrid. "The memorandum means greater security in Spain's energy supplies and it guarantees better access for our companies to Russian energy reserves."
Zapatero said Spain would make building energy ties with Russia a top priority when it takes over the European Union presidency in 2010.
Russian-EU energy relations deteriorated after a three-week spat with Ukraine in January over pricing and payment disrupted gas supplies to many countries in Europe, calling into question Russia's reliability as an EU supplier.
The Russian president played down recent rumours that talks between Sacyr and Russia's LUKOIL over the sale of the Spanish builder's 20 percent stake in Repsol had been shelved due to price differences, saying "no one has closed the door on those talks."
Zapatero added the question of whether or not talks continued between LUKOIL and Repsol "is going to depend on the companies."
Concrete business deals arising from Medvedev's official visit to Spain were limited to a gas supply agreement between Russia's Gazprom and Spain's Gas Natural to export Russian gas to Spain.
"Thanks to the swap operations, these supplies will start in the near future, initially in small volumes. We will develop the project involving the Shtokman field, which will be launched in 2014," Miller said.
The two companies have also agreed to study joint projects in northeast Europe as well as Gazprom's possible purchase of gas fired power plants in Spain, Gas Natural said in a statement.
Gas Natural has to sell 2,000 megawatts of gas fired power stations as part of the conditions for the approval of its bid to aquire Spanish power company Union Fenosa UNF.MC, which it plans to partly finance from 3 billion euros of asset sales.
Gazprom's CEO Alexei Miller told reporters in Madrid his company was also in talks with Spanish oil major Repsol over the development of Russia's Yamal gas field and the participation of Repsol in LNG-related projects.
"We will consider the possibility of Spanish companies taking part in Russian projects, including Yamal. Gazprom is in talks about such participation with companies including Repsol," Miller said.
Spain's lberdrola said on Tuesday it has signed a deal with leading Russian electricity dealer Inter Rao, to study opportunities in the Russian Federation, the EU and Latin America. (Additional reporting and writing by Jonathan Gleave; editing by James Jukwey)