Kamran Jebreili, ASSOCIATED PRESS
FILE - In this Jan. 19, 2012 file photo, fishing boats are seen in front of oil tankers on the Persian Gulf waters, south of the Strait of Hormuz, offshore the town of Ras Al Khaimah in United Arab Emirates. The European Union has announced plans to join US efforts to slow the flow of oil from Iran, the world's third largest exporter. In response, Iran has threatened to shut the Strait of Hormuz and prevent one fifth of the world's oil from reaching customers. (AP Photo/Kamran Jebreili)

"EU" and "bold action" don't often share the same sentence. But they did on Monday.

The 27 nations of the European Union dealt a huge oil shock to Iran. They agreed to ban Iranian oil to stop its rogue nuclear program. The Europeans will immediately stop signing new contracts to buy Iranian oil. Countries with existing contracts may honor them until July 1.

After that, Iran loses 18 percent of its oil export business ... or more. Some of Iran's other big oil customers — Japan and South Korea — also are scrambling to switch suppliers.

Two more words you don't often see on these pages: Bravo, EU.

The EU embargo promises to be a massive economic blow to a country already staggering from tightening U.S. and European sanctions. Iran's currency has plummeted by half against the dollar since December. Inflation rages at more than 20 percent a month. All this, before the gathering embargo.

Still, the Obama administration has been reluctant to aggressively back the European ban, fearing a huge spike in oil prices and a worldwide economic upheaval in the heart of the presidential campaign. That's a risk, yes, even though Saudi Arabia has promised to cushion any oil shock by boosting production.

We could suffer $6-a-gallon gasoline. Or not. World oil prices climbed on Monday, but the market didn't hyperventilate, even as a top Iranian leader repeated a threat to close the Strait of Hormuz, a vital shipping route for 20 percent of the world's oil.

Last month, President Barack Obama signed a law aimed at draping a giant "closed for business" sign on Iran's central bank. That bill passed the U.S. Senate 100-0. That is not a misprint. That's a show of resolve from Democrats and Republicans to stop Iran's nuclear program.

"We do mean to close down the central bank of Iran," a U.S. official recently told The New York Times. That's a refreshingly blunt statement from an administration too often leading from behind on Iran. We hope the president follows through.

Obama can show he's serious about stopping Iran by pushing the new sanctions aggressively. The law says that in June he can cut off public or private financial institutions in foreign countries that buy oil through Iran's central bank. But he could still dawdle ... the law allows him plenty of wiggle room to exempt countries from sanctions. He can also declare that there's not enough oil on the world market so ... never mind about those threats to collapse Iran's central bank.

Obama needs to make economic sanctions stick — and sting.

Financial chaos is a risk with strong sanctions. But the greater risk is allowing Iran to waltz into the nuclear club and set off a nuclear arms race in the Middle East.

Taking the risk of economic turmoil now cuts the odds that an increasingly jittery Israel strikes Iran's nuclear sites.

Iran has flimflammed the world for years now, absorbing Western diplomatic slaps while aggressively building a nuclear program that is more dangerous than ever.

Tehran now has enough nuclear fuel, with further enrichment, for about four bombs. The more Iran boosts its capacity to enrich uranium, the faster it can break out and build a nuclear arsenal.

The EU's oil embargo sends a powerful message to the mullahs: Nuclear aggression carries a painful price. The costs go up until Iran stands down.