Brussels, April 24 -- The European union on Friday cautioned that ongoing diplomatic efforts with Iran risk producing a weaker and more unstable outcome if technical expertise is sidelined, even as the United States intensifies its military presence in the Middle East.

Speaking at an informal European Council meeting in Cyprus, EU foreign policy chief Kaja Kallas warned that excluding nuclear specialists from negotiations could undermine any future agreement.

She said such an approach would likely fall short of the safeguards established under the Joint Comprehensive Plan of Action, the 2015 accord that imposed strict limits on Iran's nuclear programme in exchange for sanctions relief. Kallas stressed that a narrow focus on nuclear issues...