US President Donald Trump’s plan for a nationwide missile defense system — dubbed “Golden Dome” — faces significant technical and political challenges, and it could cost far more than he has estimated to achieve its goals.

Israeli Prime Minister Benjamin Netanyahu on Wednesday dismissed speculation of a falling out with the U.S. administration following a visit to the Gulf by U.S. President Donald Trump that left out Israel.

There was one notable — and loudly noted — absence on Wednesday at Columbia University’s graduation ceremony: detained pro-Palestinian student protest leader Mahmoud Khalil.