The United States has given Israel 30 days to increase humanitarian aid to Gaza

The United States has sent a letter to Israel demanding that it increase the delivery of humanitarian supplies to the Gaza Strip within 30 days or risk a cut in U.S. military support, according to multiple U.S. officials.

According to the New York Times and the BBC, U.S. State Department spokesman Stephen Miller confirmed on Tuesday that the letter, sent to Israeli Defense Minister Yad Galant and Strategic Affairs Minister Yad Dermer last Sunday, was signed by U.S. Defense Secretary Austin and Secretary of State Blinken.

In the letter, the United States said it was deeply concerned about the worsening humanitarian crisis in the Gaza Strip and said Israel had denied or obstructed nearly 90 percent of humanitarian operations in the north and south of Gaza in September.

It was the toughest written warning the United States has ever issued to Israel, its closest ally. Israel has not commented on the reports.

Miller said aid flows into the Gaza Strip in September were at their lowest level since a new round of fighting broke out in October. "What we have seen in the last few months is that the level of humanitarian assistance is unsustainable and has in fact fallen by more than 50 percent from its peak."

Israel is launching a new offensive in the northern Gaza Strip. The offensive is reported to have caused a large number of civilian casualties.

Israel said it was targeting Hamas positions in northern Gaza and had not stopped humanitarian aid from entering.

The Israeli Defense Ministry's Government Activities Coordination Division (COGAT), which coordinates with the Palestinians, said Monday that 30 trucks carrying aid from the World Food Program had entered northern Gaza through the Erez crossing.

Earlier, the United Nations said that northern Gaza has received no food aid for two weeks, and 400,000 Palestinians are running out of necessities to survive.

The United States is Israel's largest arms supplier, and the Israeli military has relied heavily over the past year on American warplanes, guided bombs, missiles and artillery shells to fight Hamas in the Gaza Strip.