Iran has begun payments to a Russian firm building Tehran's first atomic power plant, the company has said.
The opening of Bushehr was put back from September
The two sides had been in dispute over payments for the plant at Bushehr.
The Russian firm, Atomstroiexport, had blocked March's shipment of nuclear fuel and postponed the planned launch in September by at least two months.
Iran angrily denied falling behind with payments and said Russia was bowing to pressure from the US over its controversial nuclear programme.
The news comes after the UN Security Council on Saturday extended sanctions on Iran over the programme - banning weapons exports and freezing a number of assets.
Western nations believe Tehran is hoping to develop a nuclear arsenal, but Iran insists its nuclear programme is solely for peaceful purposes.
Atomstroiexport, a state-run company, said in a statement: "The fact that our Iranian partners have overcome their difficulties is positive."
But it added that the payment, just over half the agreed monthly instalment, was "still far" from full.
Russian officials announced in February that Iran had fallen behind.
However, Iran denied the allegation and fiercely criticised Russia for the delay, which chief nuclear negotiator Ali Larijani called "deplorable".
Mr Larijani said the delay underlined Iran's need to produce its own nuclear fuel.