The United States enacted sanctions on Monday on a Chinese company for transporting Iranian crude oil.

Chinese firm Zhuhai Zhenrong and one of its executives, Youmin Li, were targeted by the U.S. Department of the Treasury in a sign that the United States won’t tolerate any violations of U.S. sanctions on the Islamic Republic.

Beijing has said that it would defy U.S. sanctions and purchase oil from Tehran, causing U.S. Special Representative for Iran Brian Hook to say, “We will sanction any imports of Iranian crude oil.”

“There are right now no oil waivers in place,” he added. “We will sanction any illicit purchases of Iranian crude oil.”

In early May, the Trump administration ended temporary waivers to allow countries to import Iranian oil. China was one of the countries that received exemptions for importing Iranian petroleum after U.S. sanctions, including those on Iranian oil, that were lifted under the 2015 Iran nuclear deal were reimposed last November.

Since the waiver expiration, China has reportedly imported two shipments of oil from the Islamic Republic.

Fu Cong, director general of the Chinese Foreign Ministry’s Department of Arms Control, said in June, “We reject the unilateral imposition of sanctions.”

“For us, energy security is important and the importation of oil is important to Chinese energy security, and also to the livelihood of the people,” he emphasized.

“Ninety percent of Iranian crude oil has been effectively sanctioned and withdrawn from the marketplace,” U.S. Secretary of State Mike Pompeo told The Wall Street Journal on Monday.

“We don’t want to see nations think they can violate these sanctions with impunity,” he continued. “Wherever we find and identify an entity that has violated those sanctions, we will enforce.”