Containers are seen in the Port of Vigo, Spain, March 13, 2025. Photo: REUTERS/Nacho Doce

The US is weighing potential penalties against Spanish-linked shipping after Spain denied port entry to cargo vessels transporting US weapons to Israel, escalating a rare maritime and diplomatic dispute between two NATO allies.

The Federal Maritime Commission (FMC), an independent agency of the US government, opened an investigation late last year into Spain for refusing to allow at least three cargo vessels — two of which were US-flagged — into its ports.

Two of the three incidents from 2024 noted by the commission involved vessels run by the Danish shipping giant Maersk in November. The other occurred in May, when Spanish officials said they refused permission for the Danish Marianne Danica ship because it was “carrying weapons to Israel” and added they will not allow ships carrying arms for Israel to stop at its ports moving forward.

Last Friday, the FMC released a brief update on the “restrictive port practices of the government of Spain,” noting that “the policy behind those refusals remains in place.” The update went on to explain that the agency will continue its investigation, which could result in the US fining Spain up to $2.3 million per voyage if the probe concludes that the country has interfered with commerce.

“Based on the information obtained up to this point, it appears that the laws or regulations adopted, followed, or enforced by Spain are likely creating general or special conditions unfavorable to shipping in US foreign trade,” the FMC update stated. “Accordingly, the commission must also examine, and now seeks public input on, what remedial actions may be appropriate to meet or adjust those apparent conditions. The commission may weigh a range of potential remedies, including limitations on cargo, refusing entry to vessels operating under Spain’s flag, or imposing fines up to the current inflation-adjusted limit of $2,304,629 per voyage on Spanish-flagged vessels.”

The FMC also posted a more detailed notice, which was published in the Federal Register this week, explaining its concerns with Spain.

In September, Madrid announced “a multi-faceted policy aimed at halting the flow of certain cargo bound for or coming from Israel through air or marine transport,” the agency explained. “Measures it announced include banning ships and aircraft carrying weapons bound for Israel or tankers carrying fuel for use by the Israeli military from using Spanish ports and airspace.”

The agency went on to outline some of the actions it can take to combat actions it described as creating “unfavorable” conditions for US shipping.

“Remedies the commission can implement to adjust or meet unfavorable conditions to shipping in the foreign trade of the United States include adopting regulations restricting voyages to or from US ports, imposing per voyage fees, limiting amounts or types of cargo, or taking ‘any other action the commission finds necessary and appropriate to adjust or meet any condition unfavorable to shipping the foreign trade of the United States,'” the FMC said.

Spain has been one of the fiercest critics of Israel since the Palestinian terrorist group Hamas’s Oct. 7, 2023, invasion of and massacre across south Israel, amid the ensuing war in Gaza.

In one of its recent attempts to curb Israel’s defensive campaign against Hamas, Madrid decided to block US military planes and ships from using Spanish bases to transport weapons and equipment to Jerusalem.

Spain also unveiled an arms embargo and a ban on certain Israeli goods earlier this year. The Spanish government announced it would bar entry to individuals involved in what it called a “genocide against Palestinians,” block Israel-bound ships and aircraft carrying weapons from Spanish ports and airspace, and enforce an embargo on products from Israeli communities in the West Bank.

Spain has additionally canceled a €700 million ($825 million) deal for Israeli-designed rocket launchers, as the government conducts a broader review to systematically phase out Israeli weapons and technology from its armed forces.

“It is deeply concerning that Spain, a NATO member, has chosen to potentially limit US operations and to turn its back on Israel on the same day six individuals were killed in Jerusalem. These measures embolden terrorists,” a US State Department spokesperson told Reuters in September, on the same day as a Palestinian terrorist attack targeting Israelis.

Last December, FMC commissioner Louis Sola argued that Spain’s actions have a negative effect on the global system of trade, not just Israel.

“Disruptions to international trade systems not only threaten global shipping networks, but also compromise the consumer markets they support. As a member of the international maritime community, Spain is obligated to adhere to international maritime norms,” Sola said. “Reports that the government of Spain has denied access to certain US-flagged vessels raise serious concerns. Section 19 of the Merchant Marine Act, 1920, 46 U.S.C. § 42101, authorizes the commission to identify and offset unfavorable shipping conditions in US foreign trade that result from the laws or regulations of a foreign government.”