Coordinated pressure by the Obama administration and its European allies has caused a rapid fall in oil revenue to Iran, squeezing that nation’s economy ahead of nuclear talks next month, U.S. officials and industry analysts said Friday.

The financial pain is likely only to increase in the months ahead. On Friday, the White House formally certified that global oil supplies are sufficient to accommodate deeper cuts in Iranian oil imports, a technical step that clears the way for the implementation of even tougher economic sanctions set to take effect three months from now.

U.S. officials say the threat of harsher sanctions — combined with a European oil embargo scheduled to begin July 1 — is already costing Iran billions of dollars in lost revenue as the country’s traditional customers begin to turn elsewhere for petroleum. At the same time, administration officials and oil analysts say they are increasingly confident that Saudi Arabia and other suppliers can make up for Iran’s shortfall, easing the risk of global shortages and further price spikes.

“We are fully prepared to go forward with these sanctions,” a senior administration official told reporters Friday. “The best outcome here is to have the broadest number of countries working together to send a clear message to Iran.”

The new measures are intended to pressure Iran into agreeing to strict curbs on its nuclear program at negotiations set to begin in mid-April. Western officials are describing the talks as a last best chance for a diplomatic settlement of an Iranian nuclear crisis that has driven up oil prices while spurring fears of military strikes.

Countries that import Iranian oil. (The Washington Post/International Energy Agency)

The price of Brent crude rose 49 cents Friday to finish at $122.88 per barrel.

Western intelligence agencies believe that Iran is using its ostensibly civilian nuclear infrastructure to develop the components for nuclear weapons, a charge Iran vehemently denies.

The administration’s decision to press forward with deeper sanctions highlights the political risks confronting President Obama. Sharp cuts in Iranian oil could drive energy prices higher, alienating middle-class voters upon whom Obama depends for reelection.

At the same time, a failure to back painful sanctions against Iran could invite attacks by the president’s Republican rivals while also raising the risk of a unilateral military strike by Israel against Iranian nuclear facilities.

The new sanctions, signed into law in December, target the Central Bank of Iran, the financial institution that processes payments for nearly all of Iran’s foreign oil sales. One provision, set to take effect June 28, imposes sanctions on any foreign bank or company that continues to engage in oil transactions with the Iranian central bank.

The administration has granted waivers to 11 countries that have agreed to end or sharply reduce oil imports from Iran, and its diplomats are encouraging Iran’s remaining customers to agree to similar cuts. On Friday, Turkey, a major consumer of Iranian oil, announced that it would slash Iranian imports by 10 percent. Turkish officials were in talks with Saudi Arabia about making up the shortfall.

Already, the cuts have had an impact on Iran’s economy and its currency, the rial. The pressure will soon become “greater than anything Iran has faced before,” said the senior administration official, who insisted on anonymity in describing the conclusions of U.S. economic assessments.

“It is already far beyond what anyone anticipated two years ago,” the official said.

Many oil analysts predict that Iran’s exports could eventually fall by half, amounting to 1 million barrels per day, as the July embargo by the European Union kicks in and the United States pressures its allies not to buy Iranian crude.

Countries including Japan and Italy are already cutting back on purchases, and Iran’s exports fell by 300,000 barrels daily in March, according to the Swiss oil-shipping firm Petro-Logistics.

Oil prices rose slightly Friday, continuing a steady advance, and analysts said prices were likely to remain high as countries wean themselves from oil from Iran, which now exports about about 2 million barrels a day, or 2.8 percent of the global market.

Saudi Arabia has increased production by about 600,000 barrels per day since October, making up for much of the shortfall, and the U.S. Energy Information Administration estimates that OPEC spare capacity was at about 2.7 million barrels per day.

While that’s fairly low by historical standards, there are signs it might be enough for now. Global oil demand has been restrained this year, and a recent surge in oil production from North America has given the world some breathing room.

“There’s nothing in the numbers that should give government pause” about whether there’s enough capacity to make up a shortfall, said Sarah Emerson, managing principal at Energy Security Analysis.

It’s unclear just how much Iran’s exports will actually be squeezed. Much depends on whether the country can make up the drop in European and Japanese demand by selling elsewhere in the world.

“China is one of the biggest unknowns,” said David Pumphrey, an analyst at the Center for Strategic and International Studies. While China cut back on imports from Iran in February over a pricing dispute, it’s unclear whether China can continue to shun Iranian oil. Its domestic oil companies have difficulty passing on high prices to Chinese consumers, and they may find the prospect of discounted Iranian oil too good to pass up.

On the other hand, China may also be wary of flouting globally coordinated sanctions.

Other countries, meanwhile, may pick up the slack. India’s imports from Iran surged in January, and Iran may find buyers for its oil in countries such as Thailand and Burma.

From Iran’s end, the biggest calculation to make is whether the drop in exports will hurt more than the benefit it is gaining from rising oil prices as tensions flare. Last year, thanks to increasing prices, the country earned an estimated $97 billion from oil sales, according to the International Monetary Fund.

Yet a recent Reuters analysis found that Iran could see its oil revenue cut in half, by $50 billion, if exports fall to 1.5 million barrels a day and it has to sell some of its oil at a discount.

“If Iran really is forced into halving its exports, that changes the cast of negotiations” with the United States, Emerson said. “But the sanctions only work if everybody’s on board.”