The Spanish Ministry for Foreign Affairs has contacted the US government to express its unease over the recent visit by the Gibraltar Government to Washington, according to reports published in Spain.
Online publication El Confidencial Digital said news of the round of discussions in the US capital had caused upset in Madrid.
Spanish frustration at the visit was compounded by images including a photograph of Chief Minister Fabian Picardo alongside President Barack Obama and his wife Michelle.
El Confidencial Digital quoted an anonymous Spanish official as saying: “Gibraltar has scored another goal against us”.
The online publication is widely read in Spain, though it is not noted for the accuracy of its reporting and its articles must be treated with caution.