Iran’s foreign minister rejected on Thursday any new negotiation with the United States over extending the length or conditions of the 2015 nuclear accord, saying that Iran would talk about changing the accord only if every concession it made — including giving up nuclear fuel — were reconsidered.

In an interview, the foreign minister, Mohammad Javad Zarif, said that would mean Iran would retake possession of the stockpile of nuclear fuel it shipped to Russia when the accord took effect.

“Are you prepared to return to us 10 tons of enriched uranium?,” Mr. Zarif said of the relinquished stockpile — one of Iran’s biggest concessions — about 98 percent of the country’s nuclear fuel holdings.

Under the agreement, Iran retains an amount of enriched uranium too small to make a single atomic weapon.