PARIS | Tue Oct 26, 2010 - (Reuters) - LVMH (LVMH.PA) now owns 17.1 percent of luxury peer Hermes (HRMS.PA) after exercising a derivative instrument, it said on Tuesday without giving details.

A statement is expected from France's AMF market regulator on Wednesday explaining how LVMH built up its position in Hermes first to 14.2 percent and then to 17.1 percent at 80.5 euros a share, a 54 percent discount to Friday's closing price.

Hermes shares gained as much as 17 percent on Monday after LVMH announced on Saturday that it owned 14.2 percent of Hermes. This gives LVMH first-mover advantage in case any Hermes family members, who own 73 percent of the company, want to sell.

Hermes shares were down 12.2 percent at 178.15 euros by 9:43 a.m. EDT.

(Reporting by Astrid Wendlandt; Editing by James Regan)