Secretary of State Mike Pompeo on Thursday threatened a "swift and decisive" US response to any attack by Iran, in the latest of a series of escalating statements and actions.
"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," Pompeo said in a statement.
"Our restraint to this point should not be mistaken by Iran for a lack of resolve," he said.
The United States has already announced the deployment of an aircraft carrier strike group and nuclear-capable bombers to the region, saying it had information of plans for Iranian-backed attacks.
The moves have frightened some European allies as well as President Donald Trump's Democratic rivals, who fear the administration is pushing for war based on hyped-up intelligence.
Pompeo, however said: "We do not seek war."
"But Iran's 40 years of killing American soldiers, attacking American facilities, and taking American hostages is a constant reminder that we must defend ourselves," said Pompeo, referencing the 1979 Islamic revolution that transformed Iran from close US ally to sworn foe.
Iran on Wednesday said it would suspend some commitments under a 2015 nuclear accord rejected by Trump, frustrated that renewed US sanctions have prevented the country from enjoying the economic fruits of compliance with the deal.
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