Nickolay Mladenov, the top diplomat overseeing the U.S.-brokered ceasefire deal in Gaza , was in Jerusalem on Wednesday seeking to advance the ceasefire deal that Israel and Hamas agreed to more than seven months ago. His appearance comes as efforts to advance the phased ceasefire have stalled, without much progress on its key tenets, including demilitarization and reconstruction. The truce envisioned Hamas handing over its weapons, Israeli forces withdrawing and rebuilding destroyed swaths of the coastal enclave after more than two years of war. Instead, the seven months since the ceasefire have seen Israel and Hamas trade accusations of violations. Aid groups say Israel has not allowed the promised amount of aid in. Hamas has not disarmed and remains in control of roughly half the strip. Israel has stepped up its attacks in Gaza in recent days, since the U.S.-Iran ceasefire, and many Palestinians fear a return of more airstrikes and full-scale war may be imminent. Mladenov is a longtime U.N.…