U.S. officials are investigating the apparent leak of two top-secret U.S. documents that show American spy agencies tracking possible Israeli preparations for conducting an attack on Iran, three U.S. officials said.

The region has been on edge awaiting Israel’s response to an Iranian missile barrage launched on Oct. 1, which Iran said was in response to Israel’s invasion of Lebanon and the assassination of its allies, including Hamas’ Ismail Haniyeh in Tehran and Hezbollah’s…