WASHINGTON (AP) The U.S.-built pier to bring food to Gaza is facing one of its most serious challenges yet its humanitarian partner is deciding if it can safely and ethically keep delivering supplies arriving by the U.S. sea route to starving Palestinians.

The United Nations, the player with the widest reach delivering aid within Gaza, has paused its work with the pier after a June 8 operation by Israeli security forces that rescued four hostages and killed more than 270 Palestinians . Adding to the troubles, two U.S. officials said Friday that the pier would be detached again because of rough seas to prevent it from breaking apart as it did in bad weather last month.

Rushing out a mortally wounded Israeli commando after the raid, Israeli rescuers opted against returning the way they came, across a land border, Rear Adm. Daniel Hagari, an Israeli military spokesman, told reporters. Instead, they sped toward the beach and the site of the U.S. aid hub on Gazas coast, he said. An Israeli helicopter touched down near the U.S.-built pier and helped whisk away hostages and the commando, according to the U.S. and Israeli militaries.

For the U.N. and independent humanitarian groups, the event made real one of their main doubts about the U.S. sea route : whether aid workers could cooperate with the U.S. military-backed, Israeli military-secured project without violating core humanitarian principles of neutrality and independence and without risking aid workers becoming seen as U.S. and Israeli allies and, in turn, targets in their own right.

Israel and the U.S. deny that any aspect of the month-old U.S. pier was used in the Israeli raid. They say an area near it was used to fly home the hostages.