July 17 (Reuters) - European shares opened lower for a third consecutive session on Wednesday, dragged by Dutch semiconductor firm ASML on a downbeat forecast, while investors assessed potentially strict trade rules from the United States.

The pan-European STOXX 600 index was down 0.3% as of 0717 GMT, with the technology sub-index falling 1.9%.

ASML shares shed 5.3% after the chipmaking equipment supplies fell short of estimates for third-quarter sales forecast.

Adding to losses was a report saying the United States has told its allies it is considering using the most severe trade restrictions available if companies continue giving China access to advanced semiconductor technology.

Other semiconductor stocks also lost ground, including ASM International and BE Semiconductor which fell more than 2% each.

Meanwhile, Adidas gained 4.5% after the German sportswear maker increased its full-year earnings forecast after a better-than-expected second quarter. Rival Puma also added 2.5%.

Markets also eyed the final euro zone inflation data for June scheduled for release at 0900 GMT, ahead of the European Central Bank's rate-setting meeting later in the week. (Reporting by Shristi Achar A and Pranav Kashyap in Bengaluru; Editing by Varun H K)