Iran is ready to halt oil exports to the EU before sanctions over its nuclear programme can be imposed, the country's parliament said.
Angered by EU and US moves to ban Iranian oil, parliamentarians are looking to preemptively stop shipments to some European nations.
Iranian MPs said on Tuesday they would move quickly to pass a bill imposing the embargo.
Speaker Ali Larijani said that it was necessary to respond to the EU's "irrational" agression.
"In retaliation for the Zionist-backed measure of the European countries to ban Iran oil, we are ready to impose a ban on oil exports to some European countries," the government-controlled Fars news agency quoted MP Mohammad Javad Karimi-Qoddusi as saying.
"The draft bill has been almost finalised. It will oblige the government to immediately cut oil exports to the EU," another MP told Fars, according to Reuters. "The bill also will ban import of any goods from the EU."
Iran insists that its nuclear programme is peaceful, but the EU and the United States remain convinced the oil-rich nation is developing material for use in an atomic bomb.
The EU began steps to restrict Iran's ability to export crude oil in January, and its embargo on the second-largest Opec nation is set to begin in July.
The delay in imposing the ban was intended to give EU countries time to find alternative suppliers.
Iran exports 2.2m barrels of oil a day, according to the US Energy Information Administration.
About 18% of Iran's oil exports are consumed by the EU.
The US has also imposed fresh sanctions on Iran as tensions over its nuclear programme continue to grow, with President Barack Obama signing an executive order on Monday tightening loopholes on banking restrictions already in place.
Obama said in a letter to Congress that the Iranian Central Bank was hiding transactions in an attempt to avoid sanctions.
The US Treasury department said the order represented its "resolve to hold the Iranian regime accountable for its failure to meet its international obligations".
It was suggested last week by the US defence secretary that Israel could attack Iran after April in order to halt progress on its nuclear programme.
Iran's foreign ministry denounced Obama's move as "antagonistic" and said that the sanctions would make "no impact".
Ministers told the Reuters news agency: "It's psychological warfare which has no impact. ... There is nothing new, it has been going on for over 30 years."
In December 2011 Iran threatened to close the vital Strait of Hormuz, through which around 17m barrels of oil pass every day, in response to sanctions.