A letter from top U.S. officials in which they told Israel to improve Gaza's humanitarian situation or risk military aid is being reviewed by Israel, an Israeli official in Washington said late Tuesday.

"Israel takes this matter seriously and intends to address the concerns raised in this letter with our American counterparts," the Israeli official said.

The U.S. has told Israel it must take steps in the next month to improve the humanitarian situation in Gaza or face potential restrictions on U.S. military aid, according to the letter.