Russia\'s Bolshoi Theatre Thursday acknowledged that the sensational resignation of its best known dance couple had affected preparations for the premiere of the first full ballet in its restored theatre. In a battle of competing forces worthy of any ballet, world renowned soloists Ivan Vasiliev and Natalya Osipova stunned the dance world this week by announcing they were to join a lesser known Saint Petersburg theatre. The blow was all the more ill-timed as it came just days ahead of the premiere Friday of a new production of \"Sleeping Beauty\", the first full ballet in the historic theatre since it reopened last month after a six-year closure. \"I am sorry that these events have come on the eve of our production of \'Sleeping Beauty\',\" the Bolshoi ballet\'s artistic director Sergei Filin told reporters. \"This has hindered us a little from concentrating on our work.\" Osipova, 25, and her real-life partner Vasiliev, 22, announced they would be joining the Mikhailovsky Theatre in Saint Petersburg, a much smaller house which has made waves recently by focusing more on contemporary ballet. They said they harboured no hard feelings about the Bolshoi but wanted more creative freedom and were finding the fabled Moscow theatre\'s repertoire limited. But their exit has shown up considerable ill-feeling between the Bolshoi Theatre and the well-financed Mikhailovsky, whose revival coincided with the appointment of businessman Vladimir Kekhman as its director in 2007. Filin said Kekhman had phoned him this week and bluntly warned that Vasiliev and Osipova would never be allowed to perform at the Bolshoi again if it made accusations against the Mikhailovsky. Rumours have also swirled in the Russian press that Osipova -- seen by many critics as among the very greatest performing ballerinas alive -- was mightily offended to have been excluded from the cast for \"Sleeping Beauty\". Filin revealed that this was a decision of Yuri Grigorovich, the legendary 84-year-old Bolshoi ballet supremo from Soviet days who has returned to revive the production. The Kommersant newspaper wrote this week that Osipova was \"clearly not one of the maitre\'s favourites\", noting that the tireless octogenarian still had the \"decisive vote\" in the casting of his productions.