US-Spain Alliance Frays Under Iran Conflict Pressure

Why it Matters

A key U.S. ally is drifting, according to a new Congressional Research Service (CRS) report on Spain-US relations. The report lands at a precarious moment: Washington and Madrid are locked in their most serious diplomatic standoff in decades, with disputes over military basing rights, NATO defense spending, and trade threatening to unravel a partnership that has anchored U.S. strategy in southern Europe for more than 40 years.

After the U.S. began its military campaign against Iran in February 2026, Spain denied the United States access to its Rota naval base and its Morón air base. It also closed its airspace to aircraft involved in the operation. President Trump responded by calling Spain "very bad" and threatening to "cut off all trade with them."

The threat is economically significant for both countries. U.S.-Spain bilateral relations encompass nearly $75 billion in annual trade in goods and services, a trade surplus of almost $3 billion in favor of the United States, and more than $121 billion in two-way direct investment. Spanish companies alone account for 86,500 jobs on American soil. A trade rupture would hurt both sides, but the threat signals exactly how much the relationship has deteriorated.

To add to the tension, approximately 3,700 U.S. military personnel are still stationed in Spain, and four Aegis ballistic missile defense destroyers, forward-deployed at Rota since 2014, are specifically designed to defend Europe against ballistic missiles that could be launched from countries such as Iran.

The Big Picture

The CRS report, authored by Derek E. Mix, a specialist in European affairs, provides Congress with a detailed account of how a long-standing alliance frayed so quickly. The 119th Congress is being asked to consider Spain's internal political situation, its security contributions, and its economic ties in the context of oversight and legislative activities.

Spain has been a NATO member since 1982 and a European Union member since 1986. For decades, the pillars of Spanish foreign policy have included multilateral cooperation, close ties with the United States, and engagement with Latin America. That framework is now under strain from multiple directions simultaneously.

Prime Minister Pedro Sánchez, who has led Spain's government since 2018, has emerged as one of the leading European critics of the Trump Administration's foreign policy. His government's opposition to the Iran operation was framed in principled terms. In a March 2026 essay, Sánchez wrote that Spain's position "does not stem from any antipathy towards the American administration, and even less from sympathy for Iran's brutal regime," while emphasizing that "this war is illegal, a major threat to the rules-based international order, and contrary to the interests of humanity." Foreign Minister José Manuel Albares stated that Spanish military bases "will not be used for anything that falls outside the agreement with the United States and the United Nations Charter."

The bilateral Agreement on Defense Cooperation, originally signed in 1988 and amended several times since, governs U.S. access to Rota and Morón. The Spanish government's position is that the Iran operation falls outside of the agreement's scope. The Trump Administration has strongly contested that interpretation.

The Iran dispute is not the only flashpoint. Spain's government also publicly opposed the U.S. operation to capture Venezuelan President Nicolás Maduro, with Sánchez reportedly stating that Spain "did not recognize the Maduro regime" but would not recognize "an intervention that violates international law."

On defense spending, Spain stands alone within the NATO alliance. At NATO's June 2025 summit, every member except Spain committed to spending 5 percent of GDP on defense by 2035. The Sánchez government received a special exemption to set a target of 2.1 percent of GDP, arguing that contributions to the alliance should be measured not solely by spending but by military capabilities and operational participation. Trump publicly suggested Spain should be "thrown out of NATO." In August 2025, Spain announced it would not purchase U.S.-made F-35 fighter jets built by Lockheed Martin to replace its aging F-18 fleet, opting instead for a European-made alternative.

Spain's defense spending has increased significantly, from approximately $12.6 billion in 2019 to approximately $40.2 billion in 2025, crossing 2% of its GDP for the first time since 1994. The country also launched more than 30 military equipment modernization programs in 2025. Some analysts, however, have expressed doubt that Spain can meet its NATO capability requirements without further increases. Some observers attribute the government's reluctance to spend more to domestic political pressure to maintain social welfare programs.

Sánchez governs through a fragile minority coalition between his center-left Spanish Socialist Workers' Party (SSWP) and Sumar, an alliance of left-wing parties. The government depends on parliamentary support from smaller regional parties, including Catalan separatist parties whose backing was secured through a controversial 2024 amnesty law for individuals charged with crimes related to the 2017 Catalan independence crisis. The law passed Spain's Congress of Deputies by a vote of 177 to 172. The next Spanish election is due by August 2027, with the center-right Popular Party currently polling at 32 percent, compared to 28 percent for SSWP.

Political Stakes

For the Trump Administration, the Spain dispute presents a compounding set of problems. The trade threat runs into structural obstacles: Spain is an EU member, meaning any punitive trade action would almost certainly require confronting the EU as a whole rather than isolating Madrid. The administration's broader posture on European defense spending has achieved near-universal buy-in from NATO allies, but Spain's exemption disrupts that narrative.

The military dimension is more acute. The Rota base is not a peripheral asset. The Aegis destroyers stationed there operate across the Mediterranean Sea, the Black Sea, and the North Atlantic. A fifth destroyer arrived at Rota in October 2024 under a 2023 agreement to expand the forward-deployed fleet to six ships. If the bilateral basing relationship deteriorates further, the U.S. would face difficult questions about European missile defense architecture.

For Democrats and critics of the administration, the Spain episode serves a broader argument: the administration's confrontational approach to European allies is producing strategic costs that outweigh any near-term leverage gained. Spain's deliberate pivot toward China provides a concrete example. Sánchez has visited China four times in four years. Shortly after the Trump Administration announced tariffs on the EU in April 2025, Sánchez traveled to Beijing to conclude a series of trade and cooperation agreements. In November 2025, King Felipe VI visited China, and the two governments signed additional economic and cooperation agreements. In April 2026, Sánchez made yet another trip. Some analysts characterize this as a strategy to diversify Spain's economic ties in the context of U.S. pressure on trade and foreign policy.

For the Spanish public, Sánchez's posture appears to carry political utility. His government's opposition to the Iran operation and its recognition of a Palestinian state in May 2024 align with positions that polling suggests are broadly popular domestically, even as they deepen friction with Washington. Spain permanently withdrew its ambassador to Israel in March 2026 amid tensions over Spain's opposition to Israeli and U.S. strikes on Iran, a decision that further underscored the Sánchez government's foreign policy trajectory.

Spain has not abandoned its Western commitments. It has contributed $1.64 billion in military assistance and $900 million in financial and humanitarian assistance to Ukraine since January 2022, and as of December 2025 was hosting more than 259,000 Ukrainian refugees. Spanish forces participate in NATO missions in Latvia, Romania, and Slovakia, and the country contributes to NATO's training mission in Iraq, its maritime security operation in the Mediterranean, and its operation to protect Turkey's border with Syria.

The Bottom Line

The Congressional Research Service Spain report is, at its core, a warning about alliance drift. Spain remains a significant U.S. military host, a major trading partner, and an active NATO contributor, but the combination of the Iran basing dispute, the defense spending standoff, the F-35 rejection, and Spain's accelerating engagement with China illustrates a pattern.

For Congress, the report raises a direct oversight question: does the current framework governing U.S. access to Spanish military facilities adequately protect American operational interests, and if not, what legislative or diplomatic tools are available? The Spain-Europe strategic partnership that underpinned U.S. force posture in the Mediterranean for more than four decades is being tested in real time, and the outcome will have consequences well beyond the bilateral relationship.

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