European shares were subdued on Tuesday, as elevated valuations in global AI-related stocks dictated caution, while investors watched a NATO summit in Turkey for possible new government defence contracts.

The pan-European ‌STOXX 600 ⁠index ⁠was flat at 650.84 points by 0713 GMT, after closing ​below record high levels in the previous session.

The technology sector led declines, down 1.6%, with chip equipment maker ASML and semiconductor company Infineon down 4% each.

Siemens Energy lost 5.5% after brokerage Barclays downgraded ⁠the AI ‌equipment maker to "underweight" from "equal-weight."

European tech stocks were tracking a glum mood in ⁠global markets on concerns that a quarter-long rally in chip stocks had made the sector overvalued. South Korea's Samsung Electronics shares slid despite strong forecasts, while Nasdaq futures on Wall Street slipped nearly 1%. The defence sector was marginally higher, with the focus on the NATO summit, where countries ‌were anticipated to announce fresh deals in response to U.S. pressure to increase European defence spending. The sector ⁠is the top performer on the STOXX index so far this month.

Sweden's defence equipment maker Saab jumped 5.3% after brokerage Morgan Stanley upgraded the stock to "overweight" from "underweight". Among others, Shell rose 2.2% after the energy giant slightly raised its second-quarter integrated gas outlook.