Famine is quite possibly present in parts of the northern Gaza Strip, a senior U.S. State Department official said on Friday, adding that an obstacle to getting more aid to Palestinians was a scarcity of trucks in the enclave under Israeli siege.

The United Nations has warned of a looming famine and complained of obstacles to getting aid in and distributing it throughout Gaza. The U.S. also says famine is imminent, but the official on Friday told Reuters it might already be present.

The U.N.-backed global authority on food security warned earlier this month that famine was likely to occur by May in northern Gaza and could spread across the enclave of 2.3 million people by July.

U.N. spokesman Stephane Dujarric on Wednesday described “tremendous challenges” to distributing aid, including a “lack of security, lack of cooperation with the Israeli authorities, lack of insufficient number of trucks, not enough fuel.”

Israeli officials say they have increased aid access to Gaza, are not responsible for delays and that the aid delivery inside Gaza is the responsibility of the U.N. and humanitarian agencies. Israel has also accused Hamas of stealing aid.

The State Department official said one of the biggest issues limiting aid distribution was a scarcity of trucks inside Gaza and that Washington would work to help acquire or help the U.N. acquire additional trucks.

The U.N. Office for the Coordination of Humanitarian Affairs says it has more than 200 trucks for aid delivery within Gaza, including some which are heavily damaged but still operable. But ultimately the U.N. says not enough aid is getting into Gaza.

The State Department official said that in the past week there was an average of 250 aid trucks a day entering Gaza, but more were needed. The official said the U.S. was working to help get more aid regularly through Gate 96, a new entry point to reach north Gaza, citing a lack of vetted drivers.