National Security Council spokesman John Kirby said at a White House press briefing Tuesday that ships and aircraft of several nations will join the U.S. in conducting surveillance and taking defensive action against Houthi rebels who target commercial ships in the Red Sea, in what is being called, "Operation Prosperity Guardian."

Kirby told reporters during a press briefing that the Department of Defense announced the operation on Monday, calling it an international coalition of countries aimed at countering threats from the Iran-backed Houthis.

"From the beginning, we’ve said that this is an [initiative] that requires collective and international action, and we’ve been able to bring together, now, a number of partners including the United Kingdom, Bahrain, Canada, France, Italy, the Netherlands, Norway, Seychelles, Spain, and even more to address this challenge together," he said.

Kirby also said the U.S. and others – including 44 signatories including NATO, the entire European Union and G7 – condemning "in the strongest terms" the threats and acts by Houthis.

PENTAGON ANNOUNCES NEW RED SEA INTERNATIONAL MISSION TO COUNTER ESCALATING HOUTHI ATTACKS ON SHIPS

Kirby in White House briefing room

National Security Council spokesman John Kirby pauses as he is asked a question during the daily briefing at the White House in Washington, Wednesday, Oct. 11, 2023.  (AP Photo/Susan Walsh)

He explained that there are six countries that border the Red Sea, which is a conduit for 10-15% of all global trade, 8% of global grain trade and 12% of global seaborne oil trade.

Of the total trade that flows through the Red Sea, Greek-, Chinese-, Japanese- and German-owned vessels make up about 40-50% of the transits, the spokesperson said.

HERZOG SIGNALS ISRAEL READY FOR ANOTHER CEASE-FIRE IN GAZA TO FREE REMAINING HOSTAGES

A photo of the ship before the attack

This photo released by the Houthi Media Center shows Houthi escort the cargo ship Galaxy Leader on Sunday, Nov. 19, 2023. Yemen's Houthis have seized the ship in the Red Sea off the coast of Yemen after threatening to seize all vessels owned by Israeli companies.  (Houthi Media Center via AP)

"These attacks have to stop. They need to stop. They’re unacceptable," Kirby said. "The United States, our Allies and our partners will do what we have to do to counter these threats and to protect these ships."

Kirby added that a review is being conducted on whether to re-designate the Houthis as a terrorist organization, though no decision has been made, nor is a timeline available on when a decision will be made.

The Pentagon announced the establishment of Operation Prosperity Guardian earlier in the day, with U.S. Defense Secretary Lloyd Austin calling the initiative, "an important multinational security initiative under the umbrella of the Combined Maritime Forces and the leadership of its Task Force 153, which focuses on security in the Red Sea."

NETANYAHU TELLS BIDEN ISRAEL WILL ACT MILITARILY AGAINST YEMEN'S HOUTHIS IF US WON'T: REPORT

Austin speaking in Bahrain

U.S. Defense Secretary Lloyd Austin, rear, addresses members of an international maritime task force protecting commercial ships in the Red Sea at U.S. Navy Central Command headquarters in Manama, Bahrain, Tuesday, Dec. 19, 2023. Due to a sharp increase in attacks on commercial vessels transiting there in the last few weeks the U.S. has announced a new mission, Operation Prosperity Guardian, to get additional countries to send ships and intelligence support.  (AP Photo/Tara Copp)

The seriousness of the attacks, several of which have damaged vessels, has led multiple shipping companies to order their ships to hold in place and not enter the Bab el-Mandeb Strait until the security situation can be addressed. The U.S. Central Command reported two more attacks on commercial vessels on Monday. A strike by an attack drone and a ballistic missile hit a tanker off Yemen at roughly the same time a cargo ship reported an explosive detonating in the water near them, the U.S. military said.

Austin said the recent Houthi aggression "threatens the free flow of commerce, endangers innocent mariners, and violates international law."

The U.S. is still actively seeking member countries to join the mission and increase the number of navies present and participating. 

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Two U.S. Navy destroyers — USS Carney and USS Mason — are currently moving through the Bab el-Mandeb Strait to help deter and respond to attacks from the Houthis. The move to set up the expanded operation came after three commercial vessels were struck by missiles fired by Iranian-backed Houthis in Yemen on Dec. 3. 

To date, the U.S. has not struck back at the Houthis operating in Yemen or targeted any of the militants’ weapons or other sites. On Monday, Austin did not answer a question as to why the Pentagon had not conducted a counterstrike.

Fox News Digital's Danielle Wallace contributed to this report.