The US has started moving on its latest anti-Iran sanctions drive by indicating which countries might be liable to US penalties for ignoring US law on their dealings with Iran.
How quickly the US will act against uncooperative countries is not yet clear.
China and India, two of Iran’s leading crude customers, were this week left off the US list of cooperative countries.
However, the two countries face other difficulties which have affected their trade with Iran.
Japan and 10 leading European Union countries were exempted from possible US sanctions because Washington decided they were making genuine efforts to break their links with Iran despite continued oil purchases.
The EU has a ban on Iranian crude imports effective from July — Japan is cutting its imports gradually.
China and India have effectively said they will not observe US sanctions because the sanctions are not under the umbrella of the United Nations.
However, Chinese imports of Iranian crude have fallen because of an apparent dispute over contract terms, while Indian importers face difficulties insuring cargoes.
Indian companies have reportedly asked Iran if it will insure the relevant shipments and the National Iranian Oil Company has said it will consider the request.
US legislators are planning even tougher sanctions, including action against insurance companies getting involved with Iran.
Iranian officials said they are not worried about the US sanctions because they will find ways of selling their oil, But Iranian oil income is probably already affected and could drop significantly by the end of the year.