The USA stopped a shipment full of bombs hailed to Israel due to concerns it will go ahead with its ground operation in Rafah.
"As a result of that review, we have paused one shipment of weapons last week. It consists of 1,800 2,000lb bombs and 1,700 500lb bombs," the unnamed official added.
The larger 2,000lb bombs are most likely to be Mk-84s or possibly BLU-109s - or both.
The former is a cheap, general purpose munition and the latter a penetration bomb designed for use against hardened or underground targets. Both can be fitted with JDAM kits that deliver precision capability using satellite navigation. Laser guidance kits can also be fitted.
These bombs can be made to be very accurate, down to just a few metres. But in a dense, urban environment like Gaza the risk of so-called "collateral damage" is high. And that is where the concern lies. The smaller 500lb bombs can also be fitted with guidance units dropped from jets.
We do not know exactly how Israel uses these weapons, but media posts from the Israeli Air Force frequently show F-16 and F-15 jets loaded with JDAMs for strikes.
It is worth remembering that such weapons would not just be used in Gaza but also targets in southern Lebanon belonging to the Iran-backed group Hezbollah, which has been involved in almost daily cross-border exchanges of fire with Israeli forces since the start of the Gaza war.
The weapons being held back by the US are related to a future delivery, so it is unlikely to have any immediate impact. But given the rate at which Israel is bombing it will likely affect future strikes fairly soon.
A bomb shipment was halted last week over concerns Israel was going ahead with a Rafah offensive.
www.bbc.com