Secretary of State Mike Pompeo. (Andrew Harnik/AP)

The United States will allow eight countries to temporarily keep importing Iranian oil after sanctions are reimposed next week, when it will blacklist hundreds of companies and individuals, U.S. officials said Friday.

Secretary of State Mike Pompeo said the administration decided to grant the eight waivers on oil sanctions, which will be reimposed Monday, because those countries pledged to continue slashing their oil purchases from Iran. Six countries agreed to “greatly reduced” levels of oil purchases, he said, and two said they would soon end their imports of Iranian oil.

“Some of these will take a few months to get to zero,” he told reporters in a conference call on the reimposition of sanctions. “We will give them a little longer to wind down. Weeks.”

The United States is trying to force a worldwide ban on Iranian oil as it reimposes the sanctions that were suspended as part of the 2015 nuclear deal from which the United States withdrew in May. U.S. officials have vowed to block efforts to evade the prohibition by going after offenders with secondary sanctions.

Pompeo did not identify the countries and jurisdictions that will get waivers, other than to say the European Union is not among them. South Korea, Japan and India are expected to get a reprieve, however. All are among Iran’s biggest oil customers, and they have argued that stopping their purchases immediately would cause oil prices to spike worldwide.

Turkey’s Energy Ministry announced Friday that it had been notified that the United States would grant the waiver Ankara had desperately sought to keep buying oil from its neighbor. Turkey relies on oil imports for its energy, and Iran is a major source.

Treasury Secretary Steven Mnuchin said the United States is prepared to impose sanctions on SWIFT, a financial messaging system used by banks for international transactions, if Iran is allowed to use it for any purpose other than humanitarian transactions. Under the restored sanctions, Iran will still be able to purchase goods such as food, agricultural commodities, medicine and medical devices.

“But people need to be very careful these are real humanitarian transactions,” Mnuchin said.

After President Trump withdrew from the deal, which he had lambasted on the campaign trail, the United States gave countries and private businesses around the world 180 days to stop importing Iranian oil or face U.S. sanctions.

Since the Trump administration came to office, it has imposed sanctions on 168 Iranian individuals, companies and groups 19 times. On Monday, Mnuchin said, it will add 700 names. Most of them are being relisted, though 300 of them are new to the list, he said.

Though only a handful of countries support the U.S. withdrawal from the nuclear deal, unilateral sanctions are highly effective because so many oil and financial transactions are conducted at least partially using U.S. dollars.

This round of sanctions targets Iranian oil, which provides the government with 80 percent of its revenue. It also affects shipping, insurance and financial transactions.

In August, the United States resumed sanctions prohibiting transactions involving U.S. dollars, Iranian automobiles and the purchase of commercial aircraft.

The administration says it does not seek a coup against the Islamic government but aims to pressure Tehran to renegotiate the nuclear deal and change its policies, including support for militias in the region and the development of ballistic missiles. But Pompeo has outlined a dozen demands, most of them unlikely to be met by Tehran and seen by critics as a call for Iran to capitulate.

On Friday, Pompeo said the United States seeks a change in Iran’s behavior toward its own people.

“We are working toward the Iranian people having the opportunity to have the government they want,” he said, “a government that does not take their money and spend it on malign activities around the world.”

The renewed hostility has pushed the Iranian economy to the brink of collapse, as its currency has lost about 70 percent of its value. Iran’s oil imports have shrunk by about 1 million barrels a day, from a peak of 2.5 million. China has stepped up its purchases in recent months, apparently keeping them in storage.

Iran is expected to resort to subterfuge to keep its economy going. Some of its oil tankers already have turned off the electronic identity tags that keep track of where they are heading. The Europeans are establishing a special system that will essentially allow trade to continue with Iran through a form of barter, though they have had trouble getting a country to agree to host the exchange and risk U.S. sanctions.

Much of the impact of the renewed sanctions has already been baked in. Virtually all multinational corporations that do business in the United States have stopped doing business in Iran so as not to run afoul of the sanctions.

Mnuchin said he expects that the European attempt to develop an alternative system, allowing trade with Iran to continue, will ultimately fail. He and Pompeo said the United States will attempt to thwart any efforts to circumvent sanctions.