Iran has informed the United States that Washington will be held responsible for the consequences of any military action against it, the Fars news agency said on Friday.
The message was handed to the Swiss ambassador in Tehran who relayed it to Washington. Switzerland looks after the US interests in Iran as Tehran and Washington have had no diplomatic relations since 1979.
Iran's foreign ministry, which summoned the ambassador, had told the envoy that Iran was not pursuing war with the United States, reported the IRNA news agency.
Separately, the agency quoted Mohsen Baharvand, director of the Iranian foreign ministry department for the Americas, as saying: "If the side facing us take provocative and unthought-out actions, they will receive a reciprocal response whose consequences are unpredictable, and the loss and damage of it will be on all sides."
Earlier, Iranian officials told Reuters on Friday that Tehran had received a message from US President Donald Trump through Oman overnight warned that a US attack on Iran was imminent.
"In his message, Trump said he was against any war with Iran and wanted to talk to Tehran about various issues ... he gave a short period of time to get our response but Iran's immediate response was that it is up to Supreme Leader (Ali) Khamenei to decide about this issue," one of the officials told Reuters on condition of anonymity.
The second official said: "We made it clear that the leader is against any talks, but the message will be conveyed to him to make a decision ... However, we told the Omani official that any attack against Iran will have regional and international consequences."
The US said it had made plans for limited strikes on Iran in response, but then called them off.
An Iranian surface-to-air missile fired early Thursday brought down the RQ-4A Global Hawk, an unmanned aircraft with a wingspan larger than a Boeing 737 jetliner.
The shootdown has further escalated tensions between Iran the US as Tehran's nuclear deal with world powers unravels.
Iran later summoned the Swiss ambassador to Tehran to protest what it claimed was the drone’s incursion into Iranian airspace.
The US disputed that, saying the aircraft was shot down on Thursday over international waters, not inside Iranian airspace.
Later, Iranian state television's website published images it says show debris from the surveillance drone.
The pictures show what appears to be the skin of the aircraft. Iranian state television did not say where the debris was filmed.
The photographs did not show any circuit boards, wiring or electronic equipment.
