At least four of China’s state-owned oil companies have temporarily suspended purchases of Russian oil shipped by sea following new U.S. sanctions on energy giants Rosneft and Lukoil.

PetroChina, Sinopec, CNOOC and Zhenhua Oil have paused seaborne purchases of Russian crude “at least for the short term” due to fears of secondary sanctions, according to the sources.

None of the four companies responded to requests for comment from Reuters.

Neither the Russian oil companies nor the Chinese government has publicly commented on the reported suspensions.

Industry consultancies offer differing estimates of Chinese state-company imports from 250,000 barrels per day to 500,000 bpd.