Vienna, Austria ? 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 Tuesday.

Although both Russia and Iran officially say their differences are financial, the dispute has a strong political component that the West hopes could result in Moscow lining up closer behind U.S.-led efforts to slap harsher U.N. sanctions on Tehran for refusing to freeze uranium enrichment.

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 within 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 recently dropped all pretexts and bluntly told Iran that Russia would not make good on pledges to deliver nuclear fuel for Bushehr unless Tehran complies with the U.N. demand for an enrichment freeze.

Asked about the approximately 2,000 Russian workers at Bushehr, the U.S. official said: “A good number of them have left recently.”