The de-facto President of the country's biggest business conglomerate, Lee was being tried for his part in the graft case which lead to the impeachment of its President Park Geun-hye, media reported.

The preparatory trial would take place at the Central District court here from 2 pm onwards but it was unknown whether Lee would appear on Thursday as the law does not oblige him to do so.

The 48-year-old Samsung chief, who has been detained since February 17, was accused of having authorised the diversion of $37.3 million to foundations controlled by Choi Soon-sil, dubbed the "Korean Rasputin", because of her friendship with Park.

Payments were made in exchange for the South Korean public pension fund authorising a merger of two Samsung subsidiaries (one of which was owned by the fund) which would further reinforce the Lee clan's control over the group.

Aside from the bribery, Lee, who has been heading the Samsung Group since his father was disabled by a stroke in 2014, also faces charges of embezzlement and concealment of assets abroad.

Four other officials of the company, who remain at large, would also be tried alongside Lee.

The Rasputin case led to the dismissal of President Park by the South Korean Parliament in December 2016, and the Constitutional Court would announce on Friday whether or not it would ratify this decision.

If the dismissal was approved, it would strip Park of her immunity and force Presidential elections in less than 60 days.