The US is reportedly covertly providing 2,000-pound "bunker-busting" bombs to Israel's air force as Tel Aviv resumes its bombardment of the Gaza Strip following the end of a ceasefire.
Some 100 of the BLU-109 bombs - designed to penetrate concrete and other hardened surfaces to reach underground targets such as military bunkers - have been sent to Israel, according to the Wall Street Journal (WSJ).
Thousands of other munitions currently being used by Israel to kill in Gaza have also been sent, the US news outlet said.
The arms transfers, which has been conducted since 7 October, have not been disclosed publicly because of the mechanisms that are being used to transfer arms to Israel, according to US officials speaking with the WSJ.
It was not said what mechanisms were specifically being used to ensure the transfers were made undisclosed.
The Biden administration has, however, sought to legislate a congressional waiver on future arms sales to Israel as part of an additional funding package to Israel worth $14.3 billion.
US officials also said that an airstrike that hit the Jabalia refugee camp in northern Gaza earlier in the war that killed over 100 people was conducted using US provided bombs.
The covert arms transfers are occurring while the US publicly states that Israel must limit civilian casualties in its military campaign in Gaza, with US Secretary of State Anthony Blinken saying to reporters on Friday that the US was telling Israel to put "a premium on protecting civilians".
However, a +972 and Local Call investigation revealed that the Israeli military had relaxed its threshold for civilian casualties in its campaign in Gaza, allowing for the killing of hundreds of civilians when targeting Hamas officials - as occurred at the Jabalia refugee camp.
Human rights group Amnesty International has previously said that Israel has demonstrated "a chilling indifference to the catastrophic toll on civilians of their ongoing relentless bombardment of the occupied Gaza Strip".
Since the start of Israel's military campaign in Gaza, 15,207 Palestinians have been killed, the majority women and children.
A further 40,625 people have been wounded, according to Gaza's health authorities.