The security group had not previously identified the country but confirmed last night the contract was for one of Iran’s sixty airports.
Westminster added the contract has been signed, but was awaiting an exchange of board approval letters before it becomes effective.
President Trump withdrew the US from the Iran Joint Comprehensive Plan Of Action (JCPOA) at the weekend.
This has created uncertainty both in Iran and the international business community and does impact the project, the company said in a statement.
Westminster believes the services and equipment fall outside any current sanctions, adding it had also gone to great lengths to ensure compliance with international regulations and had received considerable UK Government support.
Even so, Westminster has decided to put a hold on the project while it investigates the implications for its supply chain including the potential replacement of some equipment suppliers.
Other signatories to the JCPOA - China, Russia, Germany, France and the UK - have all stated their continued support for the agreement noted Westminster.