The US State Department has issued a series of warnings today demanding that all ports in the world avoid even nominal contact with Iranian commercial ships, warning that even limited contact could lead to US sanctions.

Among the demands were that all ports and maritime insurance companies “steer clear” of Iranian ships, saying the US would sanction anyone knowingly providing service to them. The threats were even broader for Iranian oil tankers.

With respect to the tankers, even though the US offered waivers on oil purchases to eight nations, the State Department says no country must be able to allow any Iranian oil tankers to even enter their territorial waters, saying this would result in penalties and “catastrophic economic damage.”

US officials are trying to force the world to stop buying Iranian oil, but say they are also doing so while trying to avoid a major price hike. Since none of Iran’s major oil buyers is willing to stop buying, the US has so far proven unable to stop them.