The US State Department has approved the sale of 3,900 Raytheon GBU-53/B Small Diameter Bombs Increment II (SDB II) weapons to Australia for use with its Lockheed Martin F-35As.

The $815 million Foreign Military Sale package includes the 3,900 weapons, test equipment, training equipment, and other support, says the Defense Security Cooperation Agency on its web site.

"The proposed sale of SDB II supports and complements the ongoing sale of the F-35A to the Royal Australian Air Force (RAAF)," says the DSCA. "This capability will strengthen combined operations, particularly air to ground strike missions in all-weather conditions, and increase interoperability between the United States and the RAAF. Australia will have no difficulty absorbing this equipment into its armed forces."

"The proposed sale will improve Australia’s F-35 survivability and will enhance its capability to deter global threats, strengthen its homeland defense and cooperate in coalition defense initiatives," adds the DSCA.

According to Raytheon's web site, the SDB II will be fully integrated onto the F-35 by 2022, with the aircraft capable of carrying eight of the munitions internally and 16 externally.

"With the weapons carried inside, the SDB II munition will enable the F-35 to hit moving targets in adverse weather while retaining its stealth capabilities," says Raytheon.

The RAAF is committed to buying 72 F-35As, and could take its acquisition up to 100 aircraft. It's first squadron will be operational in 2021, with all 72 aircraft expected to be fully operational by 2023.

The type will replace the RAAF's Boeing F/A-18 A/B Hornets.