President Donald Trump, who seeks to prevent Iran from developing a nuclear weapon, wants to secure a new nuclear agreement with that country. Trump’s motive is honorable. Difficult diplomacy is preferable to military strikes on Iran. But numerous complications stand in the president’s way, and perhaps none of these complications is more significant than the growing threat of Iranian terrorist attacks.

Yes, formalizing a viable Iran nuclear agreement represents a big challenge in and of itself. For one, Iran has engaged in more than two decades of deceptive conduct via its covert research of nuclear warheads. Any deal would thus need to ensure prompt inspection access to any sites suspected of being used to conduct illicit nuclear weapons research. The 2015 Joint Comprehensive Plan of Action had woefully inadequate safeguards in this regard.