CADIZ, SPAIN -- Spain this week withdrew a frigate assigned to a U.S. navy task force ordered into the Persian Gulf. The decision is widely seen as reflecting persistent fears of Spain's socialist government about getting involved in a possible war with Iran.

The government of Prime Minister Pedro Sanchez made the decision despite the risk of further straining frayed relations with the United States that could endanger major U.S. defense contracts with Spain's expanding naval industry.

Spain's newest Class-100 frigate, the Mendez Nunez, was being showcased with the USS Abraham Lincoln aircraft carrier group under a cooperation agreement signed with Washington two years ago. Military relations between the United States and Spain have been governed through bilateral treaties that date back to the Cold War when the Franco government ceded important basing rights to U.S. forces, including the Rota Naval Base in Cadiz.

Spanish Defense Minister Margarita Robles said the abrupt decision to pull out of the U.S. led naval group was made for "technical reasons" over what she said was the "variation" of its original course.

But chief government spokesperson Isabel Celaa this week said the decision was based on "caution and prudence" over what she characterized as the "unpredictability" of U.S. President Donald Trump, who has made no secret the use of U.S. military force remains an option since Tehran announced that it would restart parts of its nuclear program. In announcing the evacuation of non-essential personnel from Iraq Wednesday, U.S. officials said there would be a response if Iran or its proxies target Americans.

The European Union has urged a return to the terms of an international agreement negotiated with Iran four years ago by which Tehran halted development of nuclear weapons in exchange for the suspension of economic sanctions. EU governments, including Spain, have criticized the Trump administration for re-imposing some of the sanctions based on Tehran's continued ballistic missile testing and military meddling in Iraq and Syria.

"Spain cannot accompany unilateral adventures undertaken without international authorization," said a defense analyst for Spain's official news channel RTVE, warning of possible "costs" for Spain if it became "implicated" in military actions against Iran.

The Mendez Nunez was the only European warship sailing with the U.S. force when Washington ordered the Abraham Lincoln and nine U.S. destroyers and missile cruisers into the Persian Gulf. The Spanish frigate is equipped with the AEGIS surface-to-air missile system compatible with the U.S. fleet.

The Spanish frigate remained in the Indian Ocean heading to India's port of Mumbai to await further orders from Madrid, as the U.S. ships sailed through the Straits of Hormuz earlier this week.

In a lead editorial, the conservative newspaper La Razon criticized Spain's government, claiming it was jeopardizing vital military and commercial ties with the United States to appease Iran. U.S. missions to which the Spanish government has assigned Mendez Nunez to have included maneuvers in the south China sea that risked friction with Beijing, according to the newspaper.

"American perceptions that Spain is not a country to be trusted when socialists are in power have received new impulse" said Spain's former ambassador to the United Nations, Inocencio Arias, recalling how the former socialist administration of Rodriguez Zapatero pulled Spanish troops out of Iraq after it had committed them to the U.S.-led multinational force that fought to remove Saddam Hussein in 2003.

Orders to pull Mendez Nunez appear to have come directly from Prime Minister Pedro Sanchez. Neither the U.S. embassy in Madrid nor the Spanish embassy in Washington were informed until after it was announced by the defense minister and communicated to the Pentagon, according to Spanish diplomatic sources.

Foreign Minister Josep Borrel eluded questions from reporters Wednesday, saying he did not wish to be "drawn into a quick sand."

The latest disagreement comes on the heels of other misalignments with the United States over Venezuela, Cuba, and the trade war with China.

Defense analysts question decisions to prioritize EU interests in Iran over lucrative defense contracts with the United States, which is negotiating the purchase of 20 Class-100 frigates being jointly produced by the Spanish ship builder Navantia and General Dynamics.

The United States has maintained official silence on the issue of Spain's decision to withdraw its frigate. But the situation could escalate into an open quarrel if Madrid interferes with U.S. use of its Spanish bases that would be vital in any sustained military operations against Iran.