On May 20, the same day International Criminal Court prosecutor Karim Khan made a surprise request for warrants to arrest the leaders of Israel and Hamas involved in the Gaza conflict, he suddenly cancelled a sensitive mission to collect evidence in the region, eight people with direct knowledge of the matter said.

Planning for the visit had been underway for months with U.S. officials, four of the sources said.

Khan's decision to request the warrants upended the plans backed by Washington and London for the prosecutor and his team to visit Gaza and Israel. The court was set to gather on-site evidence of war crimes and offer Israeli leaders a first opportunity to present their position and any action they were taking to respond to the allegations of war crimes, five sources with direct knowledge of the exchanges said.