The Biden administration is urging international banks not to help Russia evade sanctions, warning that firms risk losing access to markets in the United States and Europe if they support Russian businesses or oligarchs that are facing financial restrictions as a result of the war in Ukraine.

The admonition by a senior Treasury official highlights U.S. efforts to exert pressure on the Russian economy through American financial power and underscores the broad view that the Biden administration is taking of its ability to enforce sanctions as it looks to isolate Russia from the global economy.

In private meetings on Friday with representatives of international banks in New York, Adewale Adeyemo, the deputy Treasury secretary, laid out the consequences of helping Russians flout sanctions. He pointed to the “material support provision” that dictates that even if a financial institution is based in a country that has not imposed sanctions on Russia, the company can still face consequences for violating U.S. or European restrictions, including being cut off from those financial systems.

“If you provide material support to a sanctioned individual or a sanctioned entity, we can extend our sanctions regime to you and use our tools to go after you as well,” Mr. Adeyemo said in an interview on Friday. “I want to make that very clear to these institutions that are domiciled and other countries that may not have taken sanctions actions: that the United States and our allies and partners are prepared to act if they do things that violate our sanctions.”

The Biden administration has placed sweeping restrictions on Russian financial institutions, oligarchs and its central bank. It has coordinated with allies in Europe and Asia to crack down on sanctions evasion; the direct warning to foreign banks was part of that effort.

Financial institutions from China, Brazil, Ireland, Japan and Canada were at the meeting, which was hosted by the Institute of International Bankers.

Mr. Adeyemo said that U.S. banks had been careful to avoid violating American sanctions, but that Russian individuals and businesses were looking to set up trusts and use proxies as workarounds. He also pointed to firms that might be providing support to sanctioned oligarchs who are trying to move their yachts to different ports to avoid seizure.

Most jurisdictions have been complying with the sanctions, but some, such as the United Arab Emirates, have continued to provide safe haven for Russian assets. The yachts of several Russian oligarchs have been docked in Dubai.

“You’ve seen a number of Russian yachts move from ports, countries that have extended sanctions to countries that haven’t,” Mr. Adeyemo said. “We want to make clear to people that if you’re a financial institution, and you have a business that is a customer that is providing material support to one of these yachts, you, that business, could be subject to our material support provision.”

Referring to his message to foreign banks, he added: “You need to make sure that not only are you making sure that you’re watching flows into your financial institution, but you need to also help by reminding the businesses that you support that they, too, you don’t want them to be providing material support to Russian oligarchs or Russian businesses as well.”

Banks and financial institutions around the world have been grappling with how to remain in compliance with the waves of new sanctions against Russia.

Citigroup, the largest U.S. bank in Russia, with about 3,000 employees there, was in “active dialogue” to sell its Russian consumer and commercial-bank businesses, Jane Fraser, its chief executive, told Bloomberg this month.

Citigroup trimmed its exposure in Russia to $7.9 billion in March, down from $9.8 billion at the end of last year, according to a filing. “This weaponization of financial services is a very, very big deal,” Ms. Fraser said at a conference this month. She said she expected global capital flows to splinter as nations developed new financial systems to avoid being too reliant on Western firms.

Foreign banks with U.S. operations can find themselves caught between conflicting demands. In some cases, U.S. sanctions have required them to cut off longtime customers. Those who resisted doing so learned how serious the authorities could be about tracking down violators and hitting them with big fines.

In 2019, for instance, the British bank Standard Chartered paid $1.1 billion to settle cases brought by the Justice Department, Treasury, New York’s state banking regulator and state prosecutors over transactions it had carried out for Cuba, Syria, Iran and Sudan in violation of U.S. sanctions. Two years earlier, Deutsche Bank paid $630 million after it was caught helping Russian investors sneak $10 billion into Western financial centers. The international giants HSBC and BNP Paribas have also paid billions in the past 10 years to settle sanctions violations cases.

Lananh Nguyen contributed reporting.