Royal Oyster Group, one of two Dubai companies facing US sanctions over trade with Iran, says it has been unfairly targeted.
The company denied supplying oil products to Iran, saying it had merely shipped "base oils" from Iranian refineries to buyers in Oman, India and the UAE.
"We know there is no problem of exporting out of Iran, but there is a problem in importing," an executive of the shipping, contracting and oil services group told Reuters. "We were on the export side."
The US on Tuesday also announced sanctions against Speedy Ship, an affiliate of Iran's Sepahan Oil operating out of the Dubai Airport Free Zone.
Four other companies including Venezuela's national oil company Petroleos de Venezuela were included among the new entities to which Washington will apply sanctions as it tries to force Tehran to abandon its controversial uranium enrichment programme.
The US suspects Iran of secretly developing nuclear weapons. Tehran has repeatedly denied the charge, saying it is only interested civilian nuclear applications such as atomic power. The International Atomic Energy Agency, however, has been critical of Tehran for failing to allow inspections of some facilities.
Iran, an Opec member with vast reserves of oil and gas, is short of electricity and is a net importer of fuels including petrol, diesel and gas.