UPDATE 2-Russia woos Belarus with gas price cut, $10 bln loan

* Belarus gets 40 pct price cut on Russian gas

* Russia lends Belarus $10 billion for nuclear power plant

* Belarus gets 'integration discount' -- Putin

* Russia eyes closer ties in so-called Eurasian Union

* Gazprom acquires 100 pct in Belarus pipeline operator (Adds detail, quotes)

By Vladimir Soldatkin and Denis Pinchuk

GORKI, Russia, Nov 25 (Reuters) - Russia will slash gas prices for Belarus and lend Minsk $10 billion to build a nuclear plant, Prime Minister Vladimir Putin said on Friday, as he offered an "integration discount" to push his agenda of building his vision of a Eurasian Union.

Markets have closely followed talks on gas prices between the two former Soviet states as previous stand-offs between Moscow and its western neighbours have led to punishing disruptions, in winter, of Russian gas exports to Europe.

Putin said Belarus would pay $164 per 1,000 cubic metres of Russian gas in the first three months of 2012, a discount of more than 40 percent on the price it paid Russian gas export monopoly Gazprom in the third quarter of 2011.

The average price for 2012 was set at $165.6.

Russia, Belarus and Kazakhstan last week signed a declaration envisaging a Eurasian Union that would deepen their existing free-trade zone and could be joined by other ex-Soviet states.

"Belarus will get a so-called integration discount, and within the next few years it will move to pricing parity (with Russian domestic gas prices)," Putin said.

Gazprom said in a statement that in 2012 Belarus would purchase 22.5 billion cubic metres of gas, then in 2013 and 2014 it would take 23 billion cubic metres a year.

As a part of the deal, Gazprom will become a sole owner of Belarus' gas pipeline network operator Beltransgaz, acquiring a 50 percent stake it had not yet owned for $2.5 billion.

Gazprom clinched the deal just over a month before the previous agreement expires on Jan.1.

Gazprom, which expects to ship 152 billion cubic metres (bcm) of gas to Europe this year, sends around 20 percent of the fuel to the European Union through Belarus. The rest goes via Ukraine.

Earlier this month the company launched direct gas supplies to Germany at the pace of 27.5 bcm a year through the undersea Nord Stream pipeline across the Baltic.

Russia is also mulling a South Stream link on the bed of the Black Sea. The proposed pipeline is being contested by several EU-backed projects.

"Acquisition of Beltransgaz means that the transit flow of Russian gas via Belarus and Poland to Germany is likely to stay intact. The Nord Stream and South Stream pipelines will be loaded by reducing the transit via Ukraine and Slovakia," Mikhail Korchemkin, of East European Gas Analysis, said.

Gazprom, which supplies around a quarter of Europe's gas imports, has said it expected to boost gas shipments to the EU next year to 164 billion cubic metres, but the plans are facing challenges from the debt crisis in Europe and competition from cheaper fuels, including liquefied natural gas (LNG).

BUFFER ZONE

Belarus is seen in Moscow as a buffer between Russia and its Cold War-era adversary NATO and the Kremlin is keen to keep strong ties with Minsk, which suffered a financial crisis this year after Moscow jacked up its energy bill.

A balance-of-payments crisis led to a 65 percent devaluation of the Belarussian currency this year and stoked inflation, leaving the government struggling to meet its external debt obligations.

The $10 billion nuclear power project loan may help ease the funding strains facing Belarus.

A regional bailout fund will, meanwhile, decide next week on the release of a second, $440 million tranche from a $3 billion financing package that has been delayed.

Earlier this year, Russia and Belarus agreed to press ahead with a stalled plan to build a nuclear reactor near the eastern frontier of the European Union, where there are many calls to abandon nuclear energy after Japan's Fukushima nuclear disaster.

The plant, to be built in Belarus using Russian nuclear technology, will be located 50 km (31 miles) from the capital of EU member Lithuania. (Reporting by Vladimir Soldatkin; Editing by Douglas Busvine and Anthony Barker)