Iran's decision to enrich to 20% of its stock of uranium was never part of the negotiations behind the nuclear fuel swap deal Brazil and Turkey struck with Tehran last week, Brazil's foreign minister said Friday.

"That was not part--for many good reasons--because that had not happened," Celso Amorim told reporters asking how Iran's recent decision would influence world powers seeking more sanctions to curb Tehran's nuclear ambitions.

"The 20% enrichment was not part of the original proposal of the 5+1 [the permanent UN Security Council members Britain, China, France, Russia and the United States, plus Germany] and specially the Vienna Group to Iran, which was meant to build confidence," Amorim said.

"Iran, actually, had asked the agency [UN's International Atomic Energy Agency, IAEA] to get the 20% enriched uranium under the form of fuel rods. Its a right, assured by the NPT," he added, referring to the Nuclear Non-Proliferation Treaty.

"So, what happened? Some countries thought this was an opportunity to propose an agreement" like the one struck last week, Amorim said as he stood next to his Turkish counterpart Ahmed Davutoglu on the sidelines of a UN Alliance of Civilizations conference in Rio.

"Our mission was to solve this exchange of uranium. The future of the Iranian nuclear issue is between Iran and the 5+1 and Iran and the IAEA. We've opened a way for that dialogue," said the Turkish minister.

"And if Iran respects the rules of NPT and cooperates with the IAEA, Iran has the right of developing nuclear technology," Davutoglu added.

The cold reception world nuclear powers gave the nuclear swap deal, and their decision to propose a new sanctions resolution against Iran in the UN Security Council, disappointed Brazil and Turkey and has soured Washington-Brasilia relations.

The United States is pushing the U.N. resolution to punish Iran with a fourth set of sanctions after deeming that it is not doing enough to meet international demands to show its nuclear program is peaceful.