US President Donald Trump has threatened “tremendous” economic consequences for any country that helps Iran, as Washington intensifies pressure on Tehran amid the ongoing conflict.

Trump announced what he described as the “most crushing economic operation” ever imposed on a country, calling the campaign “economic warfare and isolation on an unprecedented scale”.

The US president made the announcement on Truth Social on Wednesday, warning that countries whose financial institutions, businesses, airports or government entities provide Iran with any form of economic support could also face punishment.

He did not specify what measures the affected countries would face, nor did he name any country as a target.

Trump said the campaign would target activities including oil smuggling, cash transfers, exchange houses, ship registries, front companies and financial arrangements that could provide Iran with economic support.

The announcement comes amid stalled efforts to end the conflict between the United States and Iran and reopen the Strait of Hormuz, a vital global shipping route.

According to Channels Television, the Strait remains significantly disrupted, while recent attempts to reach an agreement on reopening the corridor have failed. Trump also said on Tuesday that talks were off, despite reports that messages had continued to pass between the two sides.

The latest move further escalates Washington’s economic pressure on Tehran, which has already faced extensive US sanctions.

Iran has rejected Trump’s approach. Iranian Foreign Minister Abbas Araghchi described the latest economic pressure plan as a continuation of what he called “failed policies”, saying it would not force Tehran to surrender.

Reuters also reported that the conflict has severely disrupted global oil markets because of the impact on shipping through the Strait of Hormuz. Oil prices rose following Trump’s announcement, with traders assessing the potential effect of further restrictions on Iranian trade.

The Trump administration’s latest announcement comes as the war approaches its sixth month, with no immediate diplomatic or military resolution in sight.