By Natasha Bertrand and Oren Liebermann, CNN

(CNN) — The US and UK carried out additional strikes against Houthi targets in Yemen on Monday, marking the eighth round of attacks by the US military on the rebels’ infrastructure in just over 10 days, according to a joint statement.

They struck eight sites, according to the statement from the US and UK, which conducted the strikes, and Canada, the Netherlands, Bahrain, and Australia, which supported the attacks.

The latest strikes on Houthi targets in Yemen were “successful” and destroyed missiles, weapons storage sites and drone systems, according to a senior military official and a senior defense official.

The officials, who briefed reporters following the Monday afternoon operation, said the strikes “achieved the desired effect.”

It was a smaller number than the first joint operation on January 11 that struck over 30 Houthi targets. Monday’s strikes targeted a Houthi underground storage site and sites associates with Houthi missile and air surveillance, the statement added.

The US used fighter jets from the USS Dwight D. Eisenhower, as well as surface vessels and a submarine to strike eight locations, the senior military official said. In all, the official said approximately 25-30 precision guided munitions were fired at the targets, including Tomahawk cruise missiles.

President Joe Biden spoke to his British counterpart UK Prime Minister Rishi Sunak on Monday, the White House said earlier in the day, about a range of topics including security in the Red Sea.

“Our aim remains to de-escalate tensions and restore stability in the Red Sea, but let us reiterate our warning to Houthi leadership: we will not hesitate to defend lives and the free flow of commerce in one of the world’s most critical waterways in the face of continued threats,” the countries said in their statement.

For the first time, the US also struck an underground storage facility used by the Houthis, the official said. The storage site was assessed to have “more advanced conventional weaponry,” including missiles and one-way attack drones.

Grant Shapps, the UK’s secretary of state for defense, said four British Typhoon fighter jets took part in the strikes on Houthi targets. He warned that the ongoing Houthi launches against commercial vessels “threaten the lives of sailors and disrupt shipping at an intolerable cost to the global economy.”

Following the latest round of US and UK airstrikes in Yemen on Monday, Houthi leader Mohamed Ali al-Houthi said the strikes would only strengthen the Yemeni people.

“Your strikes will only make the Yemeni people stronger and more determined to confront you, as you are the aggressors against our country,” he said in a statement posted on X.

The rebel group said the US and the UK launched 18 airstrikes on four governorates Monday night.

CNN reported on Monday that the US has named the ongoing operation to target Houthi assets in Yemen “Operation Poseidon Archer,” suggesting a more organized and potentially long-term approach to the operations in Yemen that have been aimed at deterring the Iranian-backed group from attacking commercial vessels in the Red Sea.

The US has now struck Houthi targets in Yemen eight times since January 11, the majority of which the US military has carried out unilaterally. The first wave of strikes, in which the US and UK hit approximately 30 sites across Houthi-controlled Yemen, marked the beginning of Operation Poseidon Archer, one official said.

The attacks have targeted the Houthis’ one-way attack drones, anti-ship ballistic missiles, anti-ship cruise missiles and more as the US has tried to disrupt the group’s ability to fire on international shipping lanes.

In an attempt to avoid escalation, the officials said the latest strikes were specifically intended to target the Houthi weapons and supporting capabilities used to target international shipping lanes, describing them as similar in nature to the first round of coalition strikes against Houthi targets on January 11.

“We are not at this time expanding beyond that target set,” the senior military official said.

Deputy Pentagon press secretary Sabrina Singh said on Monday that the Houthis had not launched a new attack on commercial shipping since January 18. The Houthis claimed on Monday to have attacked a US-owned cargo ship, the M/V Ocean Jazz, but a defense official told CNN that claim was not true.

Iran’s role

Iran has been quietly fueling the attacks, US officials have said, enabling and supporting its proxy groups across the region. Tehran has been supplying the Houthis with tactical intelligence and weapons to help them target ships in the Red Sea, CNN previously reported. Iran has also continued to supply its proxy groups in Iraq and Syria, where US and coalition forces have come under attack over 150 times since October 17.

On Saturday, Iranian proxy militias launched one of their largest ballistic missile attacks since October on al-Asad airbase in Iraq, leaving two US service members with traumatic brain injuries, Singh said on Monday.

Biden acknowledged on Thursday that the US strikes were not stopping the Houthis, who have continued to target, and in some cases hit, US-owned commercial vessels operating off the coast of Yemen.

But Biden said the US airstrikes would continue, anyway. And Singh said on Monday that it would ultimately be up to the Houthis and the Iranian proxy groups when to end their attacks.

Singh said last week that the Pentagon’s initial assessments are that the strikes against the Houthis have been “very successful” in destroying “pretty much all of the targets that we hit,” leaving one less missile or capability that the Houthis can then deploy in the Red Sea.

The Houthis have said that they won’t stop their attacks until the war between Israel and Hamas inside Gaza comes to an end. Houthi leader Abdul Malek al-Houthi said in a speech on Thursday that it is “a great honor and blessing to be confronting America directly.”

Last week, the US Navy intercepted a vessel off the coast of Somalia destined for Houthi-controlled parts of Yemen that was carrying Iranian-made missile components, Central Command announced in a statement. That operation resulted in the deaths of two Navy SEALs who fell overboard while attempting to board the boat, CENTCOM said.

The US also carried out all of its strikes on Houthi targets last week unilaterally, in contrast to the coalition of countries that supported the first round of joint US and UK strikes on the Houthis on January 11.

Singh said on Thursday that future joint action wasn’t off the table, but that CENTCOM Commander Gen. Erik Kurilla had the authority to order strikes when he deemed it necessary to protect ships in the region, including US Naval assets stationed in the Red Sea. After each of the strikes the US conducted against the Houthis last week, CENTCOM said that the missiles the US destroyed were being prepared for imminent launch by the Houthis.

National Security Council coordinator for strategic communications John Kirby told reporters on Thursday that the administration is “making it harder” for the Houthis to continue their attacks with each strike on their infrastructure. And he noted that the administration has “additional options” available to it if the Houthis don’t stop. But he declined to preview what those options might look like.

“I’m not going to telegraph punches one way or another, except to say what the president said this morning– that if the Houthis continue to go down this path, we will continue to do what we can to disrupt and degrade their ability to make those choices,” he said.

“We’re not looking for a conflict with the Houthis, we’re not looking for a conflict in the region,” he added. “But we have to be able to act in our own self-defense, not just for our ships and our sailors, but for merchant ships and merchant sailors and international shipping in the Red Sea.”

CNN’s Ruba Alhenawi contributed to this report.