In a phone call with his Venezuelan counterpart, Araghchi condemned what he called "the United States' bullying approach toward Venezuela and other independent developing countries in the Western Hemisphere," according to state media.
Washington’s "threat to use force against Venezuela is a clear example of a gross violation of the fundamental principles of the UN Charter and the peremptory norms of international law," he added.
The administration of US President Donald Trump has been amassing forces in the Caribbean in the biggest military buildup in the region for decades.
Washington accuses Venezuelan President Nicolas Maduro of narco-terrorism and has offered a $50 million dollar reward for information leading to his arrest. The US strategy remains unclear but appears aimed at unseating the leftist populist.
Ties between Iran and Venezuela flourished under Maduro's predecessor Hugo Chavez and the countries continue to find common ground over objections to US policy.
Araghchi on Wednesday urged UN member states to rally against "America’s aggressive unilateralism" and accused its Mideast foe Israel of being a menace to Latin America, calling it "a major threat to the region’s peace, stability and security."
US news outlets citing US and Israeli officials reported this month that Iran's Islamic Revolutionary Guard Corps sought to kill the Israeli ambassador to Mexico but the plot was thwarted over the summer by Mexican security forces. Iran denied the allegations.