US equity futures were lower pre-bell Tuesday amid a sell-off in tech stocks and ongoing peace negotiations between US and Iran.

Dow Jones Industrial Average futures were 0.4% lower, S&P 500 futures were down 1.2%, and Nasdaq futures were 2.6% lower.

Micron Technology (MU) stock was down 6.8% in premarket activity, joining a broader sell-off in the technology sector.

Technical discussions between the US and Iran in Switzerland have been completed, with negotiating groups to be set up focusing on nuclear issues and sanctions, AFP reported, citing Iranian state media.

Iran's chief negotiator Mohammad Bagher Ghalibaf told state media that the country intends to retain control of the Strait of Hormuz after talks with the US. At least 35 vessels crossed the waterway on Monday, marking the highest level since the war in the Middle East began, AFP reported, citing data from maritime tracking firm Kpler.

Oil prices were marginally higher, with front-month global benchmark North Sea Brent crude up 0.1% at $77.61 per barrel and US West Texas Intermediate crude 0.1% higher at $73.96 per barrel.

The June S&P Global Composite Purchasing Managers' Index, due at 9:45 am ET, is seen coming in at 52.1, up from 51.5 previously, according to estimates compiled by Bloomberg. The Richmond Fed manufacturing index for June is scheduled to be released at 10 am ET.