The powerful head of Russia's largest oil company was one of seven senior officials named on a new list of US punitive measures aimed at punishing President Vladimir Putin's stance on Ukraine.
Rosneft itself did not face any new restrictions. Washington's measure freezes any holdings Sechin might have in the United States and bars him from entering the country.
BP said that it was studying what impact the US announcement might have on its 19.75-per cent holding in the state-held company.
"We are studying today's announcement in order to understand what exactly it might mean for BP."
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The British group boosted its holding in Rosneft after selling its half in the TNK-BP joint venture to the Russian firm last year.
The deal left BP head Robert Dudley holding a non-executive seat on the Rosneft board.
Sechin himself suggested with a hint of sarcasm that the sanctions reflected fears in the White House of the Russian firm preparing to conquer US production and domestic sales markets.