BP has signed a joint venture with Russian energy firm Rosneft to exploit potentially huge deposits of oil and gas in Russia's Arctic shelf.
The "strategic global alliance" will see the firms exchange expertise in exploring the region.
As part of the deal Rosneft will take 5% of BP's shares in exchange for approximately 9.5% of Rosneft's shares.
It is BP's first deal since the Deepwater Horizon spill last year, which cost it billions.
The BP shares stake is worth just under $8bn (£5bn).
"BP executives see this as the first piece of good news since that disastrous oil spill in the Gulf of Mexico last April," said the BBC's business editor Robert Peston.
But he said the deal was a controversial one, with Russia not seen as an entirely transparent society nor as as a stable place to do business.
The first oil pipeline linking the world's biggest oil producer, Russia, and the world's biggest consumer of energy, China, has begun operating.
The pipeline, running between Siberia and the northeastern Chinese city of Daqing, will allow a rapid increase in oil exports between the two countries.
Until now, Russian oil has been transported to China by rail.
Concentrated in western Siberia, Russia's network of pipelines for oil exports has so far run towards Europe.
A judge in Moscow has found former Russian oil tycoon Mikhail Khodorkovsky and his business partner guilty of corruption charges, his lawyer said Monday.
Khodorkovsky's son, Pavel, later told CNN that his father will appeal the verdict.
"Of course there will be an appeal," Pavel Khodorkovsky said. "What I'm hoping for right now is the shortest sentence possible, because I'm really hoping to see my dad as soon as possible a free man."
The trial on money laundering and embezzlement charges, which began in March 2009, was the second for the two men. Khodorkovsky could be sentenced to prison until 2017.
The US president has welcomed the US Senate's ratification of a much-delayed nuclear arms treaty with Russia.
Barack Obama said the agreement, which will pave the way for new cuts in American and Russian nuclear arsenals, was the most important such deal in almost 20 years.
After months of wrangling in the Senate, the New Start treaty was passed by a vote of 71 to 26.
Under the deal, Russia and the US will cut deployed nuclear warheads by 30%.
"This is the most significant arms control agreement in nearly two decades and it will make us safer and reduce our nuclear arsenals along with Russia," Mr Obama said.
Just 3,200 tigers now live in the wild, down from 100,000 a century ago, and those that remain face a losing battle with poachers who supply traders in India and China with tiger parts for traditional medicines and purported aphrodisiacs.
Putin, whose country is one of 13 that are home to the world's last wild tigers, hosted a "tiger summit" with Wen and representatives from other Asian countries, the highest level meeting ever held to try to save a single species.
"It is very important to save this wonderful, imperial creature -- the tiger -- for future generations," Putin said, adding its situation worldwide was approaching "catastrophe."
His spokesman Dmitry Peskov said a program to double the number of free-roaming tigers by 2022 was approved on Tuesday.