Foreign Minister Mohammad Javad Zarif warned the United States against deploying its navy in the Caribbean to disrupt Iranian fuel shipments to Venezuela.
In a letter to United Nations chief Antonio Guterres, Mohammad Javad Zarif warned against "America's movements in deploying its navy to the Caribbean in order to intervene and create disruption in (the) transfer of Iran's fuel to Venezuela."
Iran “reserves its right to take all appropriate and necessary measures and decisive action ... to secure its legitimate rights and interests against such bullying policies and unlawful practices,” Zarif wrote to Guterres.
“This hegemonic gunboat diplomacy seriously threatens freedom of international commerce and navigation and the free flow of energy,” Zarif wrote. “These efforts by the US to take coercive measures to disrupt Iran’s oil sale is a dangerous escalation.”
He said that any such action would be "illegal and a form of piracy."
The top diplomat added that the US would be responsible for "the consequences of any illegal measure."
A senior official in US President Donald Trump’s administration on Thursday said the United States was considering measures it could take in response to Iran’s shipment of fuel to Venezuela.
The official declined to specify the measures being weighed but said options would be presented to Trump.
On Thursday, the US Treasury, State Department and Coast Guard issued an advisory about sanctions-dodging tactics by countries.
Iran's Fars News Agency reported Saturday that it had received information that four US Navy warships are in the Caribbean for a "possible confrontation with Iran's tankers."
Five Iranian tankers are reportedly carrying at least $45.5 million worth of gasoline and similar products to Venezuela.
All the vessels involved belong to Iranian state-owned or state-linked companies, flying under the Iranian flag. Since a pressure campaign on Iranian vessels began, notably with the temporary seizure of an Iranian tanker last year by Gibraltar, the country's ships have been unable to fly flags of convenience of other nations, a common practice in international shipping.
TankerTrackers.com, a website focused on the oil trade at sea, first reported the ships likely were heading to Venezuela.
The capacity of the five ships is some 175,000 metric tons. On the open market, the gasoline and product carried within them would be worth at least $45.5 million.
Elliot Abrams, the US State Department's Venezuela envoy, has alleged that Caracas is paying Iran in gold to restore its troubled oil sector.
The US has imposed unilateral sanctions aimed at stopping oil exports by both Iran and Venezuela, both major crude producers.
Zarif's deputy summoned the Swiss ambassador, who represents Washington's interests in Tehran, to communicate Iran's "serious warning".
Seyyed Abbas Araqchi said any potential threat to Iran's tankers would be met with a "quick and decisive response."
He noted that Iran and Venezuela enjoy "completely legitimate and legal trade relations," adding that the US recourse to forceful or other forces of bullying measures will be seen as a threat to "free shipping, international trade and the free flow of energy."
Such measures, Araqchi said, are blatant examples of piracy and explicit violation of international laws and, as such, contravene the goals and principles enshrined in the UN Charter.
The oil sectors of Iran and Venezuela, members of OPEC, are both under US sanctions.
Venezuela has the world's largest proven oil reserves but analysts say that the sector operates below capacity. The country is in desperate need of gasoline and other refined fuel products to keep the country functioning.
Iran has also taken a hit from renewed US sanctions after Trump pulled out of a nuclear accord in 2018.
AFP, AP, Reuters and Press TV contributed to this story.