In his sternest direct threat to Tehran, US President Donald Trump has warned that a military confrontation with America would “be the official end of Iran.” Tensions between the US and Iran have been growing as the Trump administration has deployed a carrier strike group and B-52 bombers to the Gulf, citing Iranian “threats.”

The terse tweet comes amid rising fears over a potential military confrontation between the two countries. Trump administration officials are debating recent intelligence regarding whether Iran or the militias it supports are possibly planning to attack US assets in the Gulf or whether it is acting defensively in an attempt to deter US action.

Trump’s tweet marks a shift in tone after recent attempts from both sides to downplay the possibility of dangerous military conflict.

“I’m not somebody that wants to go into war, because war hurts economies, war kills people most importantly, by far most importantly,” the US President said.

Reacting to Trump stepping up his rhetoric toward Tehran, the country’s foreign minister Mohammad Javad Zarif said Monday the US President’s “genocidal taunts” will not “end Iran”.

The latest Washington-Tehran frictions come after Iran suspended its commitments under the 2015 landmark international nuclear deal, and threatened to resume production of enriched uranium which is used to make reactor fuel and nuclear weapons.

The deal aimed to cut sanctions on Iran in exchange for an end to its nuclear programme, but the US unilaterally withdrew from the agreement last year. Calling the deal “defective”, Trump then re-imposed crippling sanctions on Iran.

US Secretary of State Mike Pompeo said in a speech last year that Washington’s actions, including abandoning the nuclear deal with Tehran, were meant to force Iran behave like a “normal” country-one that doesn’t sponsor terrorism or seek to develop nuclear weapons. But many saw the address as a call for regime in everything but name. Pompeo said last week that the Trump administration doesn’t want war with Iran but warned of a “swift and decisive” response from the US, should Iran initiate an attack.

“The regime in Tehran should understand that any attacks by them or their proxies of any identity against US interests or citizens will be answered with a swift and decisive US response,” he said.