Russia is bringing home its technicians and engineers from Iran’s unfinished nuclear reactor site at a time of growing international pressure on Tehran to curb its atomic ambitions, U.S. and European representatives said on Tuesday according to the Associated Press report.

The representatives a European diplomat and a U.S. official — said a large number of Russian technicians, engineers and other specialists were flown to Moscow over the last week, around the time senior Russian and Iranian officials tried but failed to resolve differences over the nuclear reactor outside the southern city of Bushehr.

Russian officials deny links between the dispute over Bushehr and Iran’s nuclear defiance. But two senior European officials, speaking separately, said Moscow bluntly told Iran that Russia would not make good on pledges to deliver nuclear fuel unless Tehran complies with the UN demand.

Asked about the approximately 2,000 Russian workers at Bushehr, the U.S. official said: “A good number of them have left recently.” The European diplomat said a large number left last week, during abortive talks in Moscow between Russian Security Council head Igor Ivanov and Ali Hosseini Tash, Iran’s deputy Security Council chief.