Kuala Lampur, Aug. 28 -- The inability of President Donald Trump to achieve a durable breakthrough with Iran is no longer merely a Middle Eastern problem.

It is beginning to bleed directly into the already complicated relationship between the United States and China.

The warning from Beijing this week should therefore be taken seriously.

China has indicated that it could retaliate if Washington significantly expands secondary sanctions against Chinese companies doing business with Iran.

Beijing insists that its commercial relations with Tehran are legitimate and has promised to take necessary measures to protect Chinese companies and interests.

This creates an increasingly dangerous chain reaction.

The United States has been unable ...