Spain said on Tuesday it had temporarily withdrawn a frigate from a U.S.-led combat group in the Gulf amid rising tensions between Washington and Iran.
The Defence Ministry did not give reasons for the pullout of the 215-sailor Mendez Nunez from the group led by U.S. aircraft carrier USS Abraham Lincoln.
But acting defence minister Margarita Robles was to explain the motives later on Tuesday at a news conference in Brussels, a spokesman said.
The United States sent the aircraft carrier and B-52 bombers to the Middle East in a move U.S. officials said aimed to counter threats from Iran to American forces in the region.
President Donald Trump is also seeking to cut off Iran's oil exports to pressure Tehran to curb its nuclear program and its support for proxies in Syria, Iraq, Lebanon and Yemen.
While the European Union shares some U.S. concerns, including over Iran's involvement in Syria, it still backs a 2015 nuclear deal with Tehran that Trump withdrew from.
*This story was edited by Ahram Online