Nearly half of the air-to-ground munitions that Israel has used in Gaza in its war with Hamas since October 7 have been unguided, otherwise known as "dumb bombs," according to a new US intelligence assessment. The assessment, compiled by the Office of the Director of National Intelligence and described to CNN by three sources who have seen it, says that about 40-45% of the 29,000 air-to-ground munitions Israel has used have been unguided. The rest have been precision-guided munitions, the assessment says. Unguided munitions are typically less precise and can pose a greater threat to civilians, especially in such a densely populated area like Gaza. The rate at which Israel is using the dumb bombs may be contributing to the soaring civilian death toll. On Tuesday, President Joe Biden said Israel has been engaged in "indiscriminate bombing" in Gaza. Asked for comment on the assessment, IDF spokesperson Nir Dinar told CNN, "We do not address the type of munitions used." Major Keren Hajioff, an Israeli spokesperson, said on Wednesday that "as a military committed to international law and a moral code of conduct, we are devoting vast resources to minimizing harm to the civilians that Hamas has forced into the role of human shields. Our war is against Hamas, not against the people of Gaza." But experts told CNN that if Israel is using unguided munitions at the rate the US believes they are, that undercuts the Israeli claim that they are trying to minimize civilian casualties. "I'm extremely surprised and concerned," said Brian Castner, a former Explosive Ordnance Disposal (EOD) officer who now serves as Amnesty International's senior crisis adviser on arms and military operations. "It's bad enough to be using the weapons when they are precisely hitting their targets. It is a massive civilian harm problem if they do not have that accuracy, and if you can't even give a benefit of the doubt that that the weapon is actually landing where the Israeli forces intended to," Castner added. The reporting on the assessment comes at an extremely sensitive time in US-Israeli relations, as the White House struggled on Wednesday to explain Biden's comment that Israel is engaged in "indiscriminate bombing" while at the same time claiming that Israel is trying to protect civilians. A growing rift between the two countries has opened over how the Israeli military is carrying out its operations in Gaza in its war against Hamas, which it launched after Hamas killed more than 1,200 Israelis on October 7. Biden said on Tuesday that Israel is losing the support of the international community as the death toll rises in Gaza, where more than 18,000 Palestinians have been killed over the last two months, according to the Hamas-run Gaza Ministry of Health. The US is also becoming increasingly isolated internationally as it refuses to back calls for a cease-fire in the conflict. On Thursday, Biden's national security adviser Jake Sullivan begins a two-day trip to Israel, where he will meet Prime Minister Benjamin Netanyahu and will conduct "extremely serious conversations" with Israeli officials during his visit, National Security Council spokesman John Kirby said during a White House briefing Wednesday. Sullivan will discuss with the Israelis "efforts to be more surgical and more precise and to reduce harm to civilians," Kirby said. Marc Garlasco, a former United Nations military analyst and war crimes investigator who served as chief of high value targeting on the Pentagon's Joint Staff in 2003, said that using unguided munitions in a densely populated area like Gaza both greatly increases the chance that a target is missed and that civilians are harmed in the process. A US official told CNN that the US believes that the Israeli military is using the dumb bombs in conjunction with a tactic called "dive bombing," or dropping a bomb while diving steeply in a fighter jet, which the official said makes the bombs more precise because it gets it closer to its target. The official said the US believes that an unguided munition dropped via dive-bombing is similarly precise to a guided munition. But Garlasco said the Israelis "should want to use the most precise weapon that they possibly can in such a densely populated area." With an unguided munition, "there are so many variables to take into account that could lead to an incredibly different accuracy from one moment to the next," Garlasco added. The US has deliberately phased out its own use of unguided munitions over the last decade, he noted. It is not clear what kinds of unguided munitions the Israelis have been using, though experts noted that the Israeli military has been using M117 bombs that appear unguided. The Israeli Air Force posted photos of fighter aircraft armed with what looked like the M117 bombs on X in October, Castner noted. The US has also provided Israel with unguided munitions, including 5,000 Mk82 bombs, a source familiar with recent weapons transfers told CNN, confirming a Wall Street Journal report. But the US also provides Israel with systems that can transform those dumb bombs into "smart" ones, including the Joint Direct Attack Munitions guidance system and the Spice Family Gliding Bomb Assemblies. The US has provided approximately 3,000 JDAMS to Israel since October 7, CNN previously reported, and told Congress last month that it planned to transfer $320 million worth of the Spice Family kits. Kirby said on Wednesday that Israel is "doing everything they can to reduce civilian casualties." But the US has repeatedly urged Israel to be more precise and deliberate in its targeting of Hamas fighters inside Gaza, CNN has reported. Still, the Biden administration currently has no plans to place conditions on the military aid it is providing to Israel, CNN reported on Wednesday. That is despite growing calls by Democratic lawmakers and human rights organizations for the US to stop providing weapons unless Israel does more to protect civilians. A US official said that Biden ultimately believes that a strategy of quiet pressure on Israel to change its tactics has been more effective than threatening to withhold weapons. — CNN