Decision by European powers follows Iran’s failure to readmit UN inspectors to all of its nuclear sites

The UK, France and Germany are expected to announce on Thursday that they will reimpose sweeping sanctions on Iran for failing to readmit UN inspectors into all of its nuclear sites.

The decision, under consideration for months, is likely to provoke the worst crisis in Iran’s relations with the west since Israel’s attacks on the country’s nuclear sites in June. Iran is already preparing countermeasures.

The planned reimposition of the sanctions, contained in six suspended UN resolutions, will start on 18 October when the original nuclear deal signed in 2015 expires.

The move by the three European powers – known as the E3 – cannot be vetoed by permanent members of the UN security council such as Russia and China.