The United States has warned all ports and insurance companies to avoid dealing with Iranian ships. The US described the Iranian ships as a "floating liability" due to the tough new economic penalties on Tehran. Brian Hook, the State Department's special representative on Iran policy, said that the US sanctions extended to insurers and underwriters.<br />''  <br />'' He further said, knowingly providing these services to sanctioned Iranian shipping companies will result in the imposition of US sanctions. <br />''  <br />'' Since Monday, the United States has aimed to end all of Iran's sales of oil. President Donald Trump in May pulled out of an international agreement negotiated under his predecessor Barack Obama, in which Iran curtailed its nuclear program in return for sanctions relief.<br />''  <br />'' <br />