The European Union’s foreign policy chief Catherine Ashton said on Thursday she had pressed China to ensure that Chinese companies did not fill the void left by other firms leaving Iran due to U.N. sanctions.

U.S. officials said in July that Chinese companies had been pursuing trade with Iran despite the threat of U.S. sanctions and a June United Nations Security Council resolution imposing more punitive measures on Tehran over its nuclear programme.

Robert Einhorn, special adviser for non-proliferation and arms control at the U.S. State Department, said at the time that China should not “backfill” by doing more deals with Iran while “responsible countries are distancing themselves from Iran”.