WASHINGTON (Reuters) — The United States on Wednesday named seven companies that it has blacklisted for trade in Iranian petrochemicals, three based in mainland China, three in Hong Kong and one in South Africa, the State Department said in a statement.

U.S. Secretary of State Mike Pompeo had said on Tuesday the agency was targeting such entities but did not name them. His announcement appeared designed to signal that Washington would not ease its campaign of choking off Tehran’s ability to export its oil, despite appeals from China and others that it do so on humanitarian grounds because of the coronavirus outbreak.

The State Department identified the firms targeted as Hong Kong-based Mcfly Plastic Hk Ltd, Saturn Oasis Co, Sea Charming Shipping Company Ltd; Chinese companies Dalian Golden Sun Import & Export Co. Ltd., Tianyi International (Dalian) Co. Ltd. and Aoxing Ship Management (Shanghai) Ltd. and South Africa’s SPI International Proprietary Ltd.

It also said it had targeted two entities which own or control SPI International and had knowledge of its sanctionable activities: South African company Main Street 1095 and Iranian entity Armed Forces Social Security Investment Company.

Further, the agency targeted Mohammad Hassan Toulai, managing director of Iran’s Armed Forces Social Security Investment Company; Hossein Tavakkoli, director of SPI International; and Reza Ebadzadeh Semnani, director of Main Street 1095.