The US military's Central Command on Wednesday announced a major maritime interception of Iranian weapons bound for Yemen.
The January 15 seizure was conducted by US and partners' navies "along routes historically used to traffic weapons unlawfully from Iran to Yemen", Centcom said.
The US said more than 3,000 assault rifles, 578,000 rounds of ammunition and 23 advanced anti-tank guided missiles were recovered.
"An interdiction of this size is significant and much larger than many of our interdictions over the past year," Centcom spokesman Col Joe Buccino told The National.
The US supported partner forces through command and control, information sharing, and later by providing aerial and maritime assets, he added.
Also on Wednesday, Centcom congratulated Yemen on a separate seizure of 100 unmanned aerial vehicle engines bound for Houthi militants.
Centcom chief Gen Michael Kurilla called Yemen's Chief of Defence Lt Gen Saghir bin Aziz to commend the "professionalism of the Yemeni security forces" and reaffirm the command's "enduring commitment" to Middle East security.
Regional media reported an interception in eastern Al Mahra province last week while Yemeni forces were inspecting a lorry at a checkpoint.
In December, Washington accused Iran of trying to smuggle more than a million rounds of ammunition and rocket parts to Yemen, after its naval forces hauled 50 tonnes of weaponry from a fishing trawler on a key maritime smuggling route frequently used by Tehran.
The recent seizure comes as Yemeni officials hope for a breakthrough in peace negotiations.
Direct talks begin this week between the Iran-backed Houthi rebels and Saudi Arabia in a bid to negotiate an end to more than eight years of war.
