Criticisms are rising against the US Treasury Department for what lawyers say is its failure to clear up the ambiguity caused by a maze of overlapping sanctions and exemptions over Iran trade issues.

At the center of criticisms is the Department’s Office of Foreign Assets Control, known as OFAC.

Reuters has said in a report that international attorneys who regularly deal with OFAC have said the recommendations they receive from OFAC on sanctions issues relating to Iran are often vague and noncommittal.

This flies in the face of last week remarks by US Secretary of State John Kerry that traders can contact OFAC to inquire about the potential impacts of the remaining US sanctions on their Iran business plans.

Any firm concerned whether a prospective business deal with Iran would be legal, Secretary of State John Kerry said before a meeting with British bankers in London last week, should call the US agency in charge of sanctions, the Treasury Department's OFAC.

"It really shouldn't be complicated," Kerry has been quoted by Reuters as having told reporters, according to a transcript of his comments. "It's clearly defined, and when people have a question, we are available to answer those questions."

Since some sanctions were lifted, Iran has agreed to deals worth a total of at least $37 billion in sectors such as construction, aviation and car manufacturing, with companies including planemaker Airbus, carmaker Peugeot and Italian steel firm Danieli.

Dozens of other companies have said they are in talks or have signed provisional agreements with Iranian partners.

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