Iran s President Ebrahim Raisi receives Venezuelan counterpart Nicolas Maduro in Tehran. AFP
The inking of the agreement "shows the determination of the high-level officials of the two countries for development of relations in different fields," Iran's President Ebrahim Raisi said.
Maduro, speaking at a joint news conference in the Iranian capital, said the cooperation covered the energy and financial sectors as well as "work together on defence projects".
Alongside the likes of Russia, China, Cuba and Turkey, Iran is one of Venezuela's main allies. And like Venezuela it is subject to tough US sanctions.
"Venezuela has passed hard years but the determination of the people, the officials and the president of the country was that they should resist the sanctions," Raisi said during the news conference, quoted by state television.
"This is a good sign that proves to everyone that resistance will work and will force the enemy to retreat," the Iranian president added.
In addition to the 20-year accord inked by the two countries' foreign ministers, "Iran and Venezuela signed documents on cooperation in the political, cultural, tourism, economic, oil and petrochemical fields," state news agency IRNA said.
"We have important projects of cooperation between Iran and Venezuela in the fields of energy, petrochemical, oil, gas and refineries," Maduro said.
From July 18, direct flights would operate between Caracas and Tehran "in order to promote tourism and the union between our countries," he said, adding that "Venezuela is open to receive tourists from Iran".
Iran's president also emphasised the importance of direct flights between the two capitals, saying it could pave the way for the enhancement of "trade and economic relations as well as bringing the two nations closer together".
Bilateral ties between the two oil producers were strong under late Venezuelan socialist leader Hugo Chavez and have been further bolstered under his successor Maduro.
In May, Iran's Oil Minister Javad Owji met with Maduro during an official visit to Venezuela, which sits on the world's largest proven crude reserves.
Owji also met his Venezuelan counterpart Tareck El Aissami for talks on finding ways to deal with the economic sanctions imposed on both countries by the United States.
Owji's visit to Venezuela, which sits on the world's largest proven reserves of crude, came just weeks after a visit by United States officials in the midst of rising global oil prices due to the war on Ukraine.
In March, a US delegation held a hushed meeting with Maduro, whose very legitimacy as president Washington disputes.
Iran is a major oil producer and said in April that output capacity was back to levels before the reimposition of US sanctions under then president Donald Trump in 2018.
In 2020, Venezuela received two shiploads of fuel and derivatives from Iran to help address crippling domestic shortages.
Iran is the third country that Maduro has visited this week after trips to Turkey and Algeria.