Some of Britain's biggest banks will hold talks this week with John Kerry, the US Secretary of State, as they wrestle with the implications of last year's move to lift economic sanctions against Iran.
Sky News has learnt that the British Bankers' Association (BBA) has circulated a note to its members inviting them to send senior representatives to a meeting with Mr Kerry, who will be in London to attend an anti-corruption summit.
The discussions will be held against an uncertain backdrop for UK banks, some of which are keen to do more business with Tehran but remain nervous about the consequences of deals which may be frowned upon by Washington.
Mr Kerry has sought to allay concerns among foreign banks about forging new ties in Iran, saying last month that the US "is not standing in the way, and will not stand in the way, of business that is permitted in Iran since the [nuclear deal] took effect".
"There are now opportunities for foreign banks to do business with Iran.
"Unfortunately there seems to be some confusion among some foreign banks and we want to try and clarify that."
This week's meeting will take place just weeks after the banking industry's main lobbying group moved to establish a high-level panel to navigate the removal of western sanctions against Iran.
The BBA declined to comment on the invitation to its members to the meeting with Mr Kerry, but has previously confirmed to Sky News that its Iran working group was in the process of being set up.
British banks have come under pressure from the Government to expand links with Tehran ahead of a trade visit to Iran led by Sajid Javid, the Business Secretary, which is due to take place later this month.
Sources said that many BBA members, which include UK-headquartered and international banks with operations in Britain, had expressed unease about forging closer ties with Iran.
Jes Staley, the Barclays chief executive, responded to a letter from David Cameron earlier this year on the issue in which he referred to "the considerable divergence in both approach and intention between the EU, which is taking a positive approach towards Iran, and the US, where primary sanctions remain in place, thereby prohibiting US individuals or entities from engaging directly or indirectly in business related to Iran".
The Prime Minister had accused Barclays of operating "in opposition to the policy of the UK Government" by declining to process customers’ payments from Iranian entities.
UK-based exporters have complained that they have already slipped behind their competitors from France, Germany and Italy because of a lack of support from the British Embassy in Tehran, which reopened last year, having been closed since 2011
Lord Lamont, who has been appointed as the Prime Minister's trade envoy to Iran, acknowledged that the UK was trailing its European rivals.
"Britain suffered a bit because the Government not only enforced sanctions but actively discouraged even legal trade while sanctions were in place, the result was that British trade collapsed by much more than that of Germany, France, Italy," he told Sky News in an interview in February.
"Even America has exported more to Iran recently than we have."
The anxiety among some London-based bankers stems both from US lenders and American executives who work for British and other international banks.
Banks including Standard Chartered have been fined heavily for breaching sanctions against Iran in recent years.