"Shortly after taking these strikes, an additional Huthi target was struck by the US in self-defense, destroying an anti-ship cruise missile that was prepared to launch and which presented an imminent threat to vessels operating in the region," Pentagon spokesman Major General Pat Ryder said.

The additional strike occurred "probably within 15 to 30 minutes of the main operation there," Ryder told journalists.

US and British forces carried out a first wave of strikes against the Iran-backed rebel group earlier this month and followed that up with further joint strikes overnight.

The United States has also launched multiple unilateral air raids against missiles that Washington said posed imminent threats to civilian and military vessels.

Overall, "we assess that we've destroyed or degraded over 25 missile launch and deployment facilities" and have "struck unmanned aerial vehicle, coastal radar and air surveillance capabilities, as well as weapons storage areas, with good effects," Ryder said.

The Yemeni rebels began striking Red Sea shipping in November, saying they were hitting Israeli-linked vessels in support of Palestinians in Gaza, which has been ravaged by the Hamas-Israel war.

The Huthis have since declared US and British interests to be legitimate targets as well.

In addition to military action, Washington is seeking to put diplomatic and financial pressure on the Huthis, redesignating them as a terrorist organization last week after dropping that label soon after President Joe Biden took office.