As Prime Minister Benjamin Netanyahu arrives in Washington to try to repair tattered ties with President Barack Obama and defend Israeli policies, officials from US and international aid organizations say they are facing new Israeli restrictions undercutting their efforts to help Palestinians, especially Gazans trying to recover from a 50-day war in 2014.

Officials from the UN Relief and Works Agency (UNRWA) and Catholic Relief Services (CRS) told Al-Monitor that a new regulation limiting the thickness of wood planks imported into Gaza is of particular concern. Rules put in place this summer allow lumber of only a centimeter (two-fifths of an inch) thick, said Matthew McGarry, the CRS country representative for Jerusalem, the West Bank and Gaza, compared with four centimeters just a few month ago. The thinner wood, he said, is not suitable for constructing even temporary housing.

Israeli officials say that the rule was prompted by evidence that Hamas, the militant Islamic group that governs Gaza, was using the wood to build tunnels for smuggling arms and potentially fighters into Israel.

“It is preposterous to think that a state would itself supply construction materials to a terror organization that vows its own destruction,” said a statement from the Coordinator of Government Activities in the Territories (COGAT), which oversees donations and other access by international organizations to the West Bank and Gaza.