The Biden administration on Sunday froze Afghan government reserves held in U.S. bank accounts, blocking the Taliban from accessing billions of dollars held in U.S. institutions, according to two people familiar with the matter.

According to the Washington Post, the decision was made by Treasury Secretary Janet L. Yellen and officials in the Treasury Department’s Office of Foreign Assets Control, the people said. The State Department was also involved in discussions over the weekend, with officials in the White House monitoring the developments. An administration official said in a statement, “Any Central Bank assets the Afghan government have in the United States will not be made available to the Taliban.” The officials spoke on the condition of anonymity to discuss government policy not yet made public.

Cutting off access to U.S.-based reserves represents among the first in what are expected to be several crucial decisions facing the Biden administration about the economic fate of that nation following the Taliban takeover. Afghanistan is already one of the poorest countries in the world and is highly dependent on American aid that is now in jeopardy. The Biden administration is also likely to face hard choices over how to manage existing sanctions on the Taliban, which may make it difficult to deliver international humanitarian assistance to a population facing ruin, experts say.

Asked Tuesday what leverage the United States would have over the Taliban going forward, White House national security adviser Jake Sullivan said that “there are obviously issues related to sanctions” but declined to elaborate. He also said the administration would first communicate directly with the Taliban.

President Biden in his speech Monday appeared to commit to continuing to give aid to Afghanistan, saying: “We will continue to support the Afghan people. We will lead with our diplomacy, our international influence and our humanitarian aid.”

The Afghanistan central bank held $9.4 billion in reserve assets as of April, according to the International Monetary Fund. That amounts to roughly one-third of the country’s annual economic output. The vast majority of those reserves are not currently held in Afghanistan, one of the people familiar with the matter said. Among those, billions of dollars are kept in the United States, although the precise amount is unclear.

Spokespeople for the White House and Treasury Department declined to comment on the process for blocking the funds or the fate of U.S. economic assistance to Afghanistan. A spokeswoman for the Federal Reserve Bank of New York, where much of the money is presumed to be held, also declined to comment.

The United States did not need any new authority to freeze the reserves, because the Taliban was already facing sanctions under an executive order approved after the September 11, 2001, attacks, said Adam M. Smith, who served on the National Security Council and as senior adviser to the director of the Office of Foreign Assets Control during the Obama administration.

Beyond the reserves, the United States also sends roughly $3 billion per year in support for the Afghan military, or roughly 15 percent of the country’s gross domestic product. The funding can only be spent if the secretary of defense “certifies to Congress that the Afghan forces are controlled by a civilian, representative government that is committed to protecting human rights and women’s rights,” according to a congressional summary of the legislation. This funding is expected to stop flowing as well, along with smaller pots of money, such as $20 million for recruiting women to the Afghan national security forces.

About 80 percent of Afghanistan’s budget is funded by the United States and other international donors, John Sopko, the special inspector general for Afghanistan reconstruction, told Reuters in the spring. A spokesman for the White House Office of Management and Budget declined to comment on the status of congressionally approved funding for Afghanistan.

Of course, it’s dangerous,” Ian Bremmer, president and founder of Eurasia Group, a consulting firm, said about restrictions on the Afghan economy, including the freezing of funds held in the United States. “You’ll see a lot more refugees on the back of this, a lot more radicalism on the back of this. But, on the other hand, [the Afghan government] will not be able to control this country for a very long period of time. I can’t see us spending money on the Taliban.

Mark Weisbrot, co-director of the Center for Economic and Policy Research, a Washington think tank, said: “For the U.S. government to seize Afghanistan’s central bank reserves would be a big mistake. It would be telling the Taliban that the U.S. government wants to destroy them and their country’s economy.”

This is far from the first time the United States has cut off foreign governments from its assets, approving similar moves against Venezuela and Libya after leaders hostile to Washington gained power in those countries as well.