BP 'welcomed' the interest from the state company in its holding in Russia's third largest oil producer.
'This is a very good signal to the Russian and international energy markets', Russian president stressed.
Putin hails 'pragmatism and common sense' as he launches US-Russian oil project in Kara Sea, which has Saudi-scale potential.
A deal would be the biggest Chinese equity participation in onshore oil in Russia.
'The contract in current market parameters is absolutely unprecedented', Putin told investors at the annual Saint Petersburg International Economic Forum.
Officials deny any risk of atomic contamination from the site in Sakha Republic.
The Chinese media - and even more the country's social media - saw glamorous new first lady Peng Liyuan as the star of the summit.
On a visit to the Far East, he strongly hinted they should give up summer holidays to complete unfinished tasks.
More than 20 new deals on energy, investment and education are inked in Beijing.