TEL AVIV—America’s most senior intelligence and defense officials are beginning a new round of on-the-ground diplomacy aimed at resurrecting talks to release hostages still held by Hamas in Gaza and bringing Israel’s war there to a conclusion. 

CIA Director William Burns traveled to Warsaw on Monday to meet with his Israeli counterpart David Barnea, the head of Mossad, and the Qatari prime minister, according to Egyptian officials and another person familiar with the talks. The meetings are an effort to restart discussions over the hostages, a U.S. official said. The U.S. secretary of defense and chairman of the Joint Chiefs of Staff arrived in Israel for the latest discussions with the country’s war cabinet.