European stocks opened the week lower, with the STOXX 50 down 0.5% and the STOXX 600 slipping 0.1%. Oil resumed its climb after Saudi Arabia shut down a major oil pipeline following drone attacks, while a planned meeting between Iran and Gulf states was postponed. Sentiment was also pressured after major AI companies OpenAI and Anthropic called for a slower pace of development amid rising concerns about safety risks. ASML Holding fell more than 4%, Infineon dropped 6% to rank among the STOXX 600's weakest performers, while Siemens Energy declined 4.3% and Prysmian lost 5%.