The FTSE 100 opened in negative territory on Wednesday as US President Donald Trump issued a stern warning to Iran to "behave" following recent military strikes.
The remarks, reported by Cityam, have reignited investor concerns over escalating tensions in the Middle East, overshadowing earlier hopes for a diplomatic resolution.
European equity markets are trading lower, with the benchmark index under pressure from the renewed geopolitical uncertainty.
The sell-off reflects a persistent risk aversion among investors, who remain wary of any further escalation that could disrupt global supply chains or energy flows.
This marks another downturn for the index, which has struggled to find footing amid the volatile backdrop.
The latest comments from the White House come after a period of heightened activity in the region, including strikes that have drawn international condemnation.