William J. Burns was in Warsaw on Monday, where he met with the head of Mossad, Israel’s spy agency, and the prime minister of Qatar, which has helped broker talks with Hamas.
Agents worried as millions poured in. Hamas bought weapons and plotted an attack. The authorities now say the money helped lay the groundwork for the Oct. 7 assault on Israel.
Prodded by the U.S., Israel agreed to the pause in hostilities and the release of 150 imprisoned Palestinians in exchange for 50 hostages held in Gaza.
The agreement between Israel and Hamas required painful negotiations, but if carried out successfully, it could lead to the release of more hostages and extend the temporary cease-fire.