Secretary of State Hillary Clinton said Monday it could take months for new UN sanctions against Iran, as she prepared for talks in Argentina and Brazil about the perceived Iranian nuclear threat.

Speaking on the plane to Buenos Aires, the chief US diplomat appeared to back away from her contention before the US Senate last week that a new resolution could be obtained in the "next 30 to 60 days."

"We are moving expeditiously and thoroughly in the Security Council. I can't give you an exact date, but I would assume sometime in the next several months," she said before landing in the Argentine capital.

Meanwhile, a senior US diplomat in Washington dismissed Iranian reports that a Sunni militant, arrested in Iran, said his group Jundallah had received American help.

"I'm highly skeptical of those claims," the diplomatic source said, asking to remain anonymous, referring to the claims said to be made by Abdolmalek Rigi.

"There was a report over the weekend that he was moving to meet Richard Holbrooke somewhere, that's utter nonsense," the source added.

Clinton told reporters traveling with her that she expected to discuss Iran with for talks with Argentine President Cristina Kirchner, praising her stand on Iran.

"The Argentines have a very clear understanding of the dangers of the proliferation of nuclear weapons," Clinton said.

"And they have been a very strong proponent in the IAEA (International Atomic Energy Agency) against the proliferation, and have voted such even with respect to Iran. So I do expect it to come up," Clinton said.

Clinton had initially intended to meet Kirchner on the sidelines of the inauguration in Montevideo of Uruguayan President Jose Mujica, but she added Buenos Aires to her six-country Latin America tour on Sunday.

With Saturday's mammoth quake in Chile throwing her schedule into flux, Clinton decided to drop plans to spend Monday night in the Chilean capital Santiago and instead make a brief solidarity visit Tuesday to Santiago airport.

Clinton is due to travel late Tuesday to Brasilia for talks about Iran and other subjects Wednesday with President Luiz Inacio Lula da Silva and Foreign Minister Celso Amorim.

Brazil -- a current voting member on the 15-strong council but not one of the five permanent veto-wielding members -- has been reluctant to join the US push for sanctions.

She will discuss with Lula "the fact that the United States recognizes Iran has the right to peaceful civil nuclear power but does not under the nuclear non-proliferation treaty have the right to nuclear weapons.

"It is violating its international obligations, it has been found to be in violation of the International Atomic Energy Agency and the UN Security Council," she said.

"These are not findings by the United States. These are findings by the international community," she said.

"It is going to be the topic of the UN Security Council so I want to be sure he has the same understanding that we do as to how this matter is going to unfold," Clinton said.

Clinton's visit to Brazil was preceded Friday by William Burns, the undersecretary of state for political affairs, who leads US consultations among the P5-plus-1 -- the club dealing with efforts to halt Iran's contested nuclear program.

The group is made up of the five permanent veto-wielding members of the UN Security Council -- the United States, Russia, China, Britain and France -- plus Germany.

Lula at a regional summit in Mexico last week warned that the global community, in its quest for peace, should avoid isolating Iran over its controversial nuclear program.

"Peace in the world does not mean isolating someone," said Lula, whose country has its own nuclear energy program.

Brazil's Senate foreign relations committee on Thursday called Amorim to testify about the country's policy towards Iran.

Clinton's tour follows one to the oil-rich Gulf less than two weeks ago when she asked Saudi Arabia, the biggest oil exporter to China, to use its influence to persuade Beijing to join the drive for sanctions against Iran.