July 9 (Reuters) - European shares slid on Tuesday ahead of a crucial testimony from U.S. Federal Reserve Chair Jerome Powell before a congressional panel, while Indivior slipped to about three-year lows after cutting its profit forecast.

The pan-European STOXX 600 index was down 0.3% by 0707 GMT, led by losses in energy shares, tracking lower oil prices. Miners were the top gainers, rising 0.5%, as copper prices rose slightly.

All eyes will be on Powell, who is scheduled to deliver his semi-annual monetary policy testimony before Congress at 10 a.m. ET (1400 GMT).

Comments from European Central Bank board (ECB) member Piero Cipollone later in the day will also be on investors' radar to gauge the ECB's interest rate trajectory.

Among individual stocks, Dassault Systemes declined 3.7% as the French software company cut its full-year earnings target, saying its customers were being cautious with spending and were delaying the signing of contracts.

BP slipped 3.3% as it expects lower realised refining margins and weak oil trading to hurt its second-quarter earnings.

Indivior Plc lost the most among index peers, dropping 27.7% to a near three-year low after it lowered its profit forecast for the year while announcing it would discontinue sales of its schizophrenia drug Perseris and cut about 130 jobs.

(Reporting by Shubham Batra in Bengaluru; Editing by Sonia Cheema)