NEW YORK — The United Nations Security Council held an emergency session Friday to consider action against Iran days after the International Atomic Energy Agency referred Tehran over its nuclear programme amid a military stand-off in the Strait of Hormuz.

Britain, France and Germany, the three European signatories to the 2015 nuclear accord, formally requested the session. Diplomats at the IAEA in Vienna confirmed Wednesday that the agency's Board of Governors had referred Iran to the Security Council, citing repeated obstruction of inspectors and undeclared enrichment activity.

Oil markets came under pressure ahead of the session, with Brent crude trading above $100 a barrel for the first time in six weeks. The spike followed reports that Iranian Revolutionary Guard vessels shadowed commercial tankers near the strait, through which roughly a fifth of global oil supply passes.

Western diplomats briefed on the negotiations predicted Russia and China would resist any new sanctions measures, raising the prospect of deadlock. The United States signalled it would support the European push for reimposed restrictions under the accord's snapback mechanism.

Former US Ambassador Nicholas Burns described the situation as a dangerous stand-off, warning that miscalculation in the Gulf could trigger a wider confrontation. Iran's mission to the UN said any move to close the strait would be a response to Western aggression.