Repsol tried to sell a controlling stake in its Argentinian oil company to a Chinese energy group for more than $10bn before it was nationalised by Buenos Aires, according to two people familiar with the secret talks.

The attempt to sell its 57 per cent interest in YPF to the Chinese buyer, which one person involved identified as Sinopec, broke down after the Argentinian government announced on Monday that it would expropriate 51 per cent of Repsol’s holding. Repsol did not advise Buenos Aires of the discussions, which the Spanish group hoped to finalise before seeking formal endorsement from Cristina Fernández, Argentine president.

The Argentinian government holds a golden share in YPF, and any deal would have required state approval. Sinopec is already a 40 per cent partner in Repsol’s Brazilian operations. Repsol declined to comment. Sinopec could not be reached for comment.