Sales of Iranian crude oil rose by 100,000 barrels a day in January, to 1.32 million, the International Energy Agency reported on Thursday in its monthly survey, offering what appeared to be a glimpse at the initial impact of the temporary nuclear agreement that eased some of the Western sanctions against Iran.

American supporters of strong sanctions against Iran seized on the increased oil sales as new evidence that the temporary agreement, negotiated in Geneva in November and put into effect last month, had disproportionately favored Iran. The Obama administration said at the time the agreement was reached that Iran’s oil exports would not increase, remaining around one million barrels a day.

“It is clear that the Geneva negotiations and the signing of the interim agreement significantly altered the outlook for Iran’s oil market and overall economy, due to both the easing of restrictions and the reduced risks for purchasers and traders,” said Mark D. Wallace, the chief executive of United Against Nuclear Iran, a group based in New York that has supported stronger sanctions.