WASHINGTON — The United States on Monday denounced a terror tunnel discovered underneath two UN-run schools in the Gaza Strip last week.

“We strongly condemn the creation of these tunnels which are used for terrorism & recklessly put at risk the lives of students & staff,” said Jason Greenblatt, US President Donald Trump’s special envoy for international negotiations, in a tweet.

The Hamas-dug tunnel was discovered on June 1 by workers of the United Nations Relief and Works Agency for Palestine Refugees in the Near East (UNRWA) under two schools in the Maghazi refugee camp near the city of Deir al-Balah, UNRWA said.

The tunnel, between two and three meters underground, passes under the Maghazi Elementary Boys A&B School and the Maghazi Preparatory Boys School, and was built both westward into the Palestinian enclave and eastward toward the security fence with Israel, according to UNRWA.

Greenblatt, a former real estate lawyer and Orthodox Jew, has been tasked to spearhead — along with the president’s son-in-law Jared Kushner — the administration’s efforts to achieve a breakthrough on Israel-Palestinian peace, what Trump has repeatedly referred to as the “ultimate deal.”

Since Trump’s inauguration, he has gone on several “listening tours” throughout the region, where he’s spoken with multiple stakeholders in the conflict, including Prime Minister Benjamin Netanyahu, Palestinian Authority President Mahmoud Abbas and other Arab leaders.

UNRWA spokesman Christopher Gunness said last week that the tunnel “has no entry or exit points on the premises nor is it connected to the schools or other buildings in any way,” and promised it would be sealed by the UN-affiliated agency.

“UNRWA condemns the existence of such tunnels in the strongest possible terms. It is unacceptable that students and staff are placed at risk in such a way,” he added, explaining that UNRWA had “robustly intervened and protested to Hamas in Gaza.”

Hamas, for its part, denied that it or any other terror group built a tunnel under the two UN schools. The organization “strongly condemned” the UNRWA revelation, saying it would be exploited by Israel to “justify its crimes.”

US Ambassador to the UN Nikki Haley visits at a terror tunnel built by Hamas on the border of Israel with the Gaza Strip, June 8, 2017. (Matty Stern/U.S. Embassy Tel Aviv)

US Ambassador to the UN Nikki Haley visits at a terror tunnel built by Hamas on the border of Israel with the Gaza Strip, June 8, 2017. (Matty Stern/U.S. Embassy Tel Aviv)

The latest revelation came just a few days before US ambassador to the United Nations Nikki Haley visited the region. During her trip, she surveyed a Hamas-dug attack tunnel that was discovered three years ago.

Israel also voiced intense condemnation of the tunnel.

Israel’s envoy to the UN Danny Danon submitted a letter of protest to the United Nations Security Council, asking it to “strongly and unequivocally condemn Hamas and its repeated abuse of civilian infrastructure and designate this group as a terrorist organization.”

Over the years, Gaza’s Hamas rulers have built a labyrinth of tunnels, some passing under the border into Israel, which they used to launch attacks during the last conflict in 2014.

Hamas also built a vast network of tunnels under Gaza’s border with Egypt to smuggle goods and weapons. The Israeli army found and destroyed several tunnels during the 2014 war.