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President Joe Biden has issued a national security memorandum that requires countries receiving American weapons to abide by US standards.
For the first time, the administration will also be required to make annual reports to Congress on whether these requirements are being met.
The memorandum requires countries that receive US weapons to submit written assurances to the State Department that they will abide by the international laws of war and allow the entry of US humanitarian assistance.
"As a matter of policy, the United States always seeks to promote adherence to international law and encourages other states and partners to do the same," the memorandum said.
Issued on Thursday night, the memorandum comes amid growing calls from members of Mr Biden's own Democratic Party to ensure that Israel – a country that has received billions of dollars worth of US weapons – is adhering to international law in its months-long military campaign in Gaza.
Since October 7, about 28,000 Palestinians, the majority of the civilians, have been killed by Israeli strikes.
Entire neighbourhoods have been reduced to rubble, causing widespread concerns that international law is being breached.
Israel has also been carrying out strikes in Khan Younis and Rafah, cities in southern Gaza that the military forced more than one million Palestinian civilians to flee to, saying they would be safe.
Mr Biden, who has expressed firm support for Israel's right to defend itself against Hamas, has twice bypassed Congress to expedite weapons sales for Israel.
Displaced Palestinians find refuge in Gaza cemetery – video
On December 9, the Biden administration approved the sale of about 14,000 rounds of tank ammunition to Israel, worth more than $106 million, without congressional approval.
The President made a similar move on December 29, approving $147.5 million in sales of military equipment, again without input from Congress.
Democratic Senator from Maryland Chris Van Hollen had led a similar push to condition foreign aid on following international law. His proposed amendment won the support of 18 other senators.
"This is huge," he said in a thread on X, formerly Twitter. "It’s the first time ever that these types of transparency and accountability mechanisms will be enforced on US security assistance."
The US is Israel's top donor and nearly all aid to Israel last year – in excess of $3.8 billion – was for defence purposes.
But with the war dragging on and the Palestinian death toll continuing to mount, Mr Biden, who is running for re-election, is growing increasingly frustrated.
On Wednesday, Israel's Prime Minister Benjamin Netanyahu rejected a Hamas proposal for a ceasefire that would have paused fighting and enabled the release of dozens of hostages, and said he intends to launch a ground operation in Rafah.
The Biden administration said on Thursday it would not support a major military campaign in Rafah and Mr Biden levelled his strongest criticism at Israel since the war began, saying the actions of its military have been “over the top”.
Latest from the Israel-Gaza war – in pictures
