Secretary of State Rex Tillerson’s team on Monday won a breakthrough in its effort with Saudi Arabia to ease a humanitarian crisis in war-torn Yemen.

Four American mobile cranes arrived in Hudaydah, Yemen, where they will be used to offload food and other aid supplies from ships at port. The city had been blockaded by a Saudi-led coalition, which has been fighting against Iran-backed rebels who overthrew the previous government.

“No one should ever have to live the way the people of Yemen are living,” U.S. Ambassador to the United Nations Nikki Haley said Monday. “We thank our partners who helped us make this delivery possible so that we can help the tens of millions of innocent people who wake up each day facing hunger and disease.”

The war in Yemen has become a theater of conflict in a broader rivalry between Saudi Arabia and Iran. The Houthi rebels toppled the central government in 2015 and maintained their position with the support of Iran. That conflict continues to escalate, as the Saudis have been criticized for killing civilians in indiscriminate bombing campaigns and the Houthis have fired missiles at Riyadh, the capital of Saudi Arabia, and killed the former Yemeni president in December.

The fighting also has become a flashpoint between the United States and Iran, as President Trump’s team has accused Iran of violating United Nations resolutions by providing the Houthis with the ballistic missiles that were fired into Saudi Arabia.

“The Iranians are not supposed to be exporting any missiles or any related material,” Haley said. “And they are allowing missiles like this to be fired over [at] innocent civilians, and that is what has to stop.”

Such violations have contributed to Trump’s interest in withdrawing from the Iran nuclear agreement negotiated by former President Barack Obama’s administration, even as the Trump administration supports Saudi Arabia taking aggressive steps to confront Iran. But Saudi tactics in Yemen have led to a loss of some American support, especially among officials who blame them for the humanitarian crisis.

“We call on all sides of the conflict to allow full access for humanitarian and commercial supplies, including fuel, by keeping the country’s ports open and allowing humanitarian agencies to deliver aid without interference,” Haley said.