Department of Defense of the United States is "worried" about Ukraine asking for GLSDB bombs because "the timeline for deploying the weapons could take far too long," writes Foreign Policy with reference to its sources in the department.
Back in November 2022, Boeing company proposed the Pentagon to start supplying Ground-Launched Small Diameter Bomb, a high-precision ammunition that can be fired from M142 HIMARS or M270 rocket launchers at a distance up to 150 km.
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But the decision to transfer them has not been issued yet, and the reason is not the fear of "escalation" as it was with ATACMS long-range rockets:
"Instead, officials inside the Office of the Secretary of Defense and the U.S. Air Force are concerned that the long lead time to deploy the SDB could render the weapons redundant given the fast pace of fighting in Ukraine," according to the media.
Experts estimated that Ukraine could get two launchers and 24 weapons within nine months after the Pentagon approves the plan, and 12 launchers and 750 bombs by the end of 2024. As things are, even if the U.S. approves the supplies today, the first bombs will reach the frontlines not sooner than autumn.

On the other hand, if the war lasts longer, these bombs still have a chance to become a difference maker for the Armed Forces of Ukraine. Foreign Policy notes that Boeing declined to comment on the issue, while the Ukrainian officials hope all the "internal impediments" would be solved and expect to receive the precision bombs in the next package of U.S. military aid.

As a reminder, the GLSDB bomb is a combination of an M26 unguided rocket and a guided air bomb.
GBU-38 version of this bomb can destroy a target more than 150 km from the deployment location, which is almost twice as far as a GMLRS rocket actively used by the Ukrainian forces with HIMARS and M270.
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