United States President, Donald Trump issued a stern warning to Iran, suggesting it will be destroyed if a conflict breaks out between the two countries.
"If Iran wants to fight, that will be the official end of Iran," he said in a tweet on Sunday. "Never threaten the United States again!"
The United States has deployed additional warships and planes to the Gulf in recent days.
But Trump's tweet marks a shift in tone after recent attempts to downplay the possibility of military conflict.
In an interview with Fox News broadcast on Sunday, the president vowed that he would not let Iran develop nuclear weapons but said he did not want a conflict.
"I'm not somebody that wants to go into war, because war hurts economies, war kills people most importantly - by far most importantly," he said.
Iran has also moved to talk down concerns over the escalating tensions. On Saturday, its foreign minister insisted there was no appetite for war.
"There will not be a war since neither we want war nor does anyone have the illusion they can confront Iran in the region," Mohammad Javad Zarif told state news agency Irna.
And on Sunday Iran's Fars news agency reported that the commander of the elite Islamic Revolution Guards Corps, Maj Gen Hossein Salami, also said Iran was not seeking a conflict - but added that the US was "afraid of war and don't have the will for it".