While investors are still assessing the full impact of the USA withdrawal from the nuclear accord, UBS Group AG said the sanctions could cut Iran's oil exports by as much as 500,000 barrels a day in the next six months.
Bruno Le Maire said Europe should not act as "vassals" to the U.S. or accept that it is the "world's economic policeman".
"We want to reinforce this regulation and incorporate the recent decisions taken by the United States", Le Maire said.
Analysts and officials say Trump threatens to create all by himself the kind of split between allies that Russian Federation and China have tried and failed to foster for years, with Europe now relying on Moscow and Beijing to keep the Iran deal alive.
European governments tried for months to persuade Mr Trump to stick with the deal but failed, and now fear it will raise the risk of conflict in the region.
Some refiners and oil traders are already starting to look for alternatives to Iranian barrels.
French Foreign Minister, Jean-Yves le Drian has now waded into the debate after President Macron phoned his Iranian counterpart, Hassan Rouhani, insisting Paris was determined to preserve the nuclear deal, but it equally expected Tehran to respect its own obligations.
Even the USA needs global partners, she cautioned, saying: "No country is big enough to face this world alone".
Saudi Arabia immediately pledged to help offset the loss of Iranian crude, saying it "remains committed to supporting the stability of oil markets, benefiting producers and consumers alike".
Merkel: Europe can't rely on USA protection anymore
While European Union countries have made progress on defence cooperation, the effort remains "in its infancy", she said. Speaking after Merkel, Macron said that "We should not be waiting, we must do something right now".
The pact's signing had been planned for long time, but the move coincides with the US move to re-impose sanctions against Iran that have rattled USA allies.
President Donald Trump's decision will likely most hurt aircraft makers, oil companies and auto manufacturers.
Since the Iran nuclear accord was struck in 2015, it has been mostly European companies that moved back in to sign deals with Iran.
German Chancellor Angela Merkel warned this week that Europe could no longer rely on the United States to "protect" it, while French President Emmanuel Macron said that "we cannot let others decide for us".
"As the sanctions relief introduced by the USA pursuant to the JCPOA focused to a large extent on the relaxation of secondary sanctions and thus permitted non-US persons to trade more freely with Iran, the re-imposition of these secondary sanctions will have the opposite effect", it said.
However, Le Maire acknowledged he has "no illusions" that he'll get what he asked for.
It said it will comply with any sanctions.
In the US, the Energy Information Administration reported nationwide crude inventories slid 2.2 million barrels last week, in contrast to a forecast for a 1 million-barrel gain in a Bloomberg survey.
Le Maire proposed creating a European body that would have the same kind of powers that the US Justice Department has to punish foreign companies for their trade practices.