Jason Greenblatt, the United States' Middle East envoy, slammed on Sunday the militant group Hamas's use of Iranian "blood money" for weapons and tunnels to attack Israel.Following the revelation that Israel had foiled an attempt to smuggle explosive material hidden inside medical supplies into the Gaza Strip, Greenblatt took to Twitter to angrily condemn Iranian funding of terror and Hamas's use of these funds to finance attacks on Israel."Hamas should be improving the lives of those it purports to govern, but instead chooses to increase violence and cause misery for the people of Gaza," the US envoy wrote. "Imagine what the people of Gaza could do with the $100 million Iran gives Hamas annually that Hamas uses for weapons and tunnels to attack Israel!"Greenblatt also condemned Iranian funding of terror across the Middle East, stating that the money should be invested domestically."Iran spends almost a billion dollars a year sponsoring terrorism in Lebanon, Israel and West Bank/Gaza. This blood money only increases violence and does nothing to help the Palestinian people," Greenblatt wrote. "The corrupt regime in Tehran squanders the resources of the Iranian people on military adventures throughout the region instead of investing at home and promoting peace abroad."The US envoy also called on Hamas to release Israeli civilians and the remains of fallen soldiers held in the Gaza Strip."Hamas must also permit the repatriation of Hadar Goldin’s remains and the release of Oron Shaul, as well as the release of Israeli civilians - Avraham Abera Mengistu, Hisham al-Sayed and Juma Ibrahim Abu Ghanima," he wrote.Last week, amid Palestinian threats not to engage with the US as a Middle East mediator, Greenblatt twice warned the Palestinians not to walk away from efforts to restart frozen Israeli-Palestinian peace talks.“It is easy to walk away from the table but that helps no one and reduces or perhaps even eliminates the chances of achieving a comprehensive peace agreement, and that would be terrible for the Palestinian people,” Greenblatt told the annual conference of the Institute for National Security Studies in Tel Aviv.On Tuesday, Greenblatt refused to tell a closed meeting of EU ambassadors in Israel when the US would present its prospective Middle East peace plan.