(Adds Ulyukayev's lawyer, details, background)
MOSCOW, Nov 22 (Reuters) - A Russian judge summoned the boss of the country's biggest oil company to testify next week in the trial of a former economy minister accused of taking a bribe from him, after Rosneft CEO Igor Sechin failed to appear in court on Wednesday.
Sechin, a close ally of President Vladimir Putin, is a key witness in the trial of Alexei Ulyukayev, who was arrested last year after a late night meeting in Sechin's office.
Ulyukayev faces up to 15 years in prison, accused of accepting $2 million from Sechin in return for approving the sale of a state-controlled oil company to Rosneft. Police swooped on him inside Rosneft headquarters shortly after Sechin handed him the cash.
Ulyukayev denies the accusations and says he was framed by Sechin. His lawyers say their client cannot testify in court before Sechin's testimony as a witness.
"All of us are here thanks to witness Sechin," Ulyukayev's lawyer Timofei Gridnev told the court after Sechin failed to appear on Wednesday. Gridnev said it was the third time Sechin had ignored a summons to appear.
Judge Larisa Semyonova read out a letter from Sechin's lawyers saying he would be unable to attend for the rest of the year due to his tight schedule, but she nevertheless summoned him for next Monday.
Before his arrest, Ulyukayev was one of the leading figures in a faction of economic liberals who argued for less state control over the economy.
Sechin is widely seen as the main champion of the opposite view, that the state should consolidate its grip, particularly over the energy sector that provides a large share of Russia's state revenue through its two biggest companies, Rosneft and Gazprom.
Ulyukayev had opposed last year's sale of the medium-sized oil company Bashneft to Rosneft. Prosecutors say he signed off on the deal and then took the cash from Sechin.
Sechin missed Wednesday's hearings because he is on a business trip to western Siberia, where on Tuesday he attended the opening of a new Rosneft oil field.
On Wednesday, he met a regional governor and chaired a meeting with Rosneft's management in the Siberian city of Khanty-Mansiisk, Rosneft said. (Reporting by Polina Nikolskaya; Additional reporting by Vladimir Soldatkin; Writing by Dmitry Solovyov; Editing by Polina Devitt and Peter Graff)