In defiance of threats by Washington, the first of five Iranian oil tankers heading to Venezuela entered the country's waters.

It is carrying more than a million barrels of fuel.

The U.S., which has imposed sanctions on both Venezuela and Iran, says it is monitoring the convoy. Both Caracas and Tehran have warned Washington not to interfere with the delivery.

Amid heightened tensions over what Venezuelan authorities described as threats from the United States, the oil vessel Fortune officially entered Venezuela's Exclusive Economic Zone (EEZ) at about 7:30 pm local time (11:30 GMT) on Saturday, according to the shipping tracker TankerTracker.

"The first Iranian tanker reached the Venezuelan coasts," the Iranian embassy in Venezuela said in a Twitter post. "Grateful to the Bolivarian Armed Forces for escorting them."

Venezuelan television showed images of a navy ship and aircraft preparing to meet it. The government of President Nicolas Maduro had pledged the military would escort the tankers once they reached the EEZ.

Fortune was heading to the El Palito refinery in Puerto Cabello in northern Carabobo state, according to the television.

The rest of the Iranian ships - the Forest, Petunia, Faxon, and Clavel - are expected to arrive in the coming days.

The shipments have caused a diplomatic standoff between the U.S., Iran, and Venezuela, which are both under harsh U.S. economic sanctions. 

The U.S. recently beefed up its naval presence in the Caribbean for what it said was an expanded anti-drug operation. Pentagon spokesman Jonathan Hoffman said on Thursday he was not aware of any operations related to the Iranian vessels.
In a televised address, Maduro said, "We have the right to trade freely."

He added, "Venezuela and Iran both want peace." 

'Defiance to hegemony'

Mohammad Marandi, a professor at the University of Tehran, said the United States has no right to dictate how two nations conduct their business.

"What is important is that these are trade ties between two sovereign countries, and the regime in Washington is in no position to dictate terms to the international community," Marandi told Al Jazeera.

"Iran is not a weak country like countries within the EU that bow down to the United States when it makes it mad. Sending five ships is a big message - it wasn't just one or two - so the Iranians did that both to give support to the Venezuelan people to prevent them from suffering, and also in an act of defiance to U.S. hegemony."

Iranian President Hassan Rouhani had on Saturday warned the U.S. against disrupting the shipments as the oil tankers passed through the Caribbean Sea on their way to Venezuela.

"If the Americans cause problems for our oil tankers in the Caribbean Sea, we will also cause problems for them," Rouhani said in a telephone call with Qatar's Emir Sheikh Tamim bin Hamad Al Thani. 

Rouhani stressed that Iran did not want a new conflict with the U.S., but his country would reserve the right to defend its interests. 

"We, therefore, hope that the Americans will not make a mistake in this regard," said the president, according to comments published on his office's web portal.

The tanker flotilla is reportedly carrying about 1.53 million barrels of gasoline and alkylate to Venezuela.

The fuel from Iran comes at a time when the shortage of gasoline in Venezuela, chronic for years in some parts of the country, has worsened during the coronavirus pandemic.

The two nations held a close relationship since late Venezuelan President Hugo Chavez took power in 1999.