Sechin was called to court to testify but has missed the first two court sittings since then. In a letter to the court, his lawyer said Sechin's schedule would become tighter by the end of this year.

Ulyukayev is on trial on charges of extorting a $2 million bribe from Sechin, in exchange for Ulyukayev's approval of a business deal. Ulyukayev denies the charges.

(Reporting by Polina Nikolskaya; writing by Dmitry Solovyov; editing by Polina Devitt)