Iran warns 'equal countermeasure' steps if US tries to block oil exports

Iran says it will respond with equal countermeasures if the United States tries to block its oil exports.

"If America wants to take a serious step in this direction it will definitely be met with a reaction and equal countermeasures from Iran," said foreign ministry spokesman Bahram Qassemi. 

The statement comes as US officials step up diplomatic efforts to pressure countries to stop importing Iranian oil.

Washington is attempting to force Tehran to change its behaviour by cutting its oil exports to zero. 

Brian Hook, the senior official leading negotiations with US allies on a new Iran strategy, said Washington is confident the world has enough spare oil capacity to replace Iranian crude.

Iranian President Hassan Rouhani in return warned that regional oil supply could be jeopardised if the US managed to get its allies to stop buying Tehran's oil.

Supreme Leader Ayatollah Ali Khamenei on Saturday backed President Rouhani's suggestion that Iran might block Gulf oil exports if its own exports are stopped.

Already fraught relations between Tehran and Washington have worsened in recent days, and tensions continued to mount between Donald Trump and Iran as a war of words exploded over Twitter. 

Trump tweeted a warning to Rouhani late on Sunday, with an all capital letters tweet that sparked questions about Washington's strategy towards the Islamic republic.

— Donald J. Trump (@realDonaldTrump) July 23, 2018

A few hours later, Iranian Foreign Minister Mohammad Javad Zarif fired back.

— Javad Zarif (@JZarif) July 23, 2018

The US is regularly suspected of backing the idea of regime change, but analysts say its current stance may simply be an attempt to pivot after a week of dire headlines over Trump's much-maligned summit with Russia's Vladimir Putin and a relative lack of progress on North Korea.

While Trump's "tough stand" was hailed by Israeli Prime Minister Binyamin Netanyahu, it also provoked an avalanche of questions about its exact meaning and impact.

When asked about the president's motivations, White House spokeswoman Sarah Sanders said he was focused on "the safety and security of the American people" and ensuring Tehran did not acquire nuclear weapons.

But she seemed to downplay concerns about his aggressive posturing, saying Trump has been "pretty strong since day one in his language toward Iran."

Iran has faced the threat of US sanctions since Trump decided in May to withdraw the United States from a 2015 agreement between world powers and Iran over its disputed nuclear programme.

Agencies contributed to this report