The United States has imposed sanctions on a network of Chinese, Emirati, and other companies that it accused of helping to deliver and sell Iranian petroleum and petrochemical products to East Asia.<br />'' <br />'' The U.S. Treasury Department yesterday said that the network of people and entities had used a web of Gulf-based front companies to facilitate the delivery and sale of hundreds of millions of dollars in products from Iranian firms to China and elsewhere in East Asia.<br />'' <br />'' A media report says Washington has increasingly targeted Chinese companies over the export of Iran's petrochemicals as the prospects of reviving the nuclear pact have dimmed.<br />'' <br />'' In Doha, Qatar last week, indirect talks between Tehran and Washington ended without a breakthrough over how to salvage the deal, under which Iran had reined in its atomic program.<br />'' <br />''The U.S. State Department also targeted a Vietnamese company and a Singapore-based company for engaging in the transport of Iranian petroleum products. Three Iran-based entities were also targeted in the action.