The initiative came from Congressman Joe Pitts, who suggested that "governments across the globe should be isolating the Russian Navy, not accommodating it," despite the fact that letting Russian vessels into their ports is perfectly legal and does not violate domestic or international law.
Madrid has been singled out as the key "wrongdoer."
The newly added measure, Pitts argued, "is particularly important in the case of Spain, who, although a cherished NATO ally, grants Russia access to the ports in its enclaves across the strategically important strait of Gibraltar, where the United Kingdom has a Permanent Joint Operating Base that hosts US ships."
Spain has indeed allowed more than 50 Russian ships, including warships, submarines and amphibious vessels, to refuel and resupply at its port city of Ceuta since 2011. The city bordering Morocco is located less than 20 miles away from Gibraltar, a small British overseas territory claimed by Spain.
Apart from Spain, Pitts also mentioned Greece, another NATO member, as well as Malta, Cuba, Venezuela and Nicaragua.
"I hope this amendment will cause governments to think twice before offering up their ports to Putin's navy," he added.