United Nations officials worked feverishly to avert a humanitarian crisis in Yemen by trying to broker an emergency deal to curtail a Saudi-backed military offensive targeting the country’s most important port, people familiar with the efforts said.

As airstrikes by the Saudi-led coalition rattled the Red Sea port and Iran-backed Houthi fighters tried to retain their hold on the city, U.N. officials sought to persuade both sides to accept a deal to prevent a full-scale assault that could cripple Hodeidah port, which serves as the gateway for three-quarters of the humanitarian aid and commercial goods flowing into Yemen.

“We continue to use every opportunity to avoid military confrontation in Hodeidah,” said Martin Griffiths, the U.N. special envoy for Yemen. “I also call on the parties to exercise restraint and to give peace a chance.”

U.N. talks faltered early Wednesday when Houthi fighters refused to accept a deal that would have required them to cede control of the city to a third party, people familiar with the talks said.

Soon after, residents reported hearing dozens of airstrikes in and around the port, marking the launch of a military campaign, named Golden Victory.