The Departments of State and Defense on Friday said they could not compile enough evidence to prove that Israel used American arms in violation of international humanitarian law, according to a new report ordered by President Joe Biden.
The report was mandated by National Security Memorandum 20 to examine the use of U.S.-supplied arms in active conflict zones.
"We do not have complete information to verify whether US defense articles covered under NSM-20 were specifically used in actions that have been alleged as violations of [international humanitarian law] or international human rights law during the period of the report," the report said. "The nature of the conflict in Gaza makes it difficult to address or reach conclusive findings on individual incidents."
However, the assessment continues to say that given "Israel's significant reliance on U.S.-made defense articles" that it is "reasonable to assess" that some have been used in instances "inconsistent" with Israel's obligation under international law.
MORE: Israel-Gaza live updates: Delegations leave Cairo without cease-fire dealWhile the report says the Israeli government has "the knowledge, experience and tools" to implement "best practices for mitigating civilian harm," the high number of civilian casualties "raise substantial questions about whether the [Israel Defense Forces] is using them effectively in all cases."
Additionally, the report notes that Israel did not cooperate with U.S. efforts to ramp up humanitarian aid and distribution in Gaza during the initial months of the conflict, but that officials have observed improvements.
Though it says the level of assistance reaching Palestinians is still not sufficient, the report says the administration "does not currently assess that the Israeli government is prohibiting or otherwise restricting the transport or delivery of U.S. humanitarian assistance" as defined by U.S. law under the Foreign Assistance Act.
A document summarizing the critical findings of the report also noted that the NSM-20 was a useful tool toward inducing Israel to take steps to increase aid for Gaza.
As it pertains to Israel, the report covers the period from Oct. 7 to late April. It also examines other U.S. security partners involved in armed conflicts, such as Ukraine.
The State Department noted that the administration relied heavily on information from Israel to compile its findings, but that the nature of the conflict in Gaza also made uncovering information difficult.
Israeli officials were briefed on the contents of the NSM-20 report around the time it was given to Congress, according to a senior Biden administration official.
Sen. Chris Van Hollen, a Maryland Democrat, said that while the administration's report on Israel's weapons use made some "important general findings," the report "ducked" major questions about compliance with international law.
Van Hollen has been an outspoken critic of Israel's military operations in Gaza and has repeatedly pushed President Biden to get tougher on Israel over humanitarian concerns.
"The one important general finding that was made in this report was the conclusion that there are reasonable grounds to believe that the Netanyahu government has violated international law in its conduct in Gaza," Van Hollen told reporters. "But the administration ducked all the hard questions about making the actual determination."
ABC News' Allison Pecorin contributed to this report.