TEHRAN, Iran - Iran delivered a resolute message Sunday on the eve of talks with six world powers: We're mining our own uranium now, so there is no stopping our nuclear ambitions.

The Islamic Republic said it had produced its first batch of domestically mined uranium ore for enrichment, meaning it does not have to rely on foreign suppliers for a process that the West fears is geared to producing nuclear arms.

Despite U.N. sanctions over the program, "our nuclear activities will proceed, and they will witness greater achievements in the future," Iranian nuclear chief Ali Salehi told state-run Press TV.

Western officials downplayed the announcement, saying that it had been expected and that Iran did not have enough ore to maintain the large-scale enrichment program that Tehran says it is building as a source of fuel for an envisioned network of nuclear reactors.

"Given that Iran's own supply of uranium is not enough for a peaceful nuclear-energy program, this calls into further question Iran's intentions and raises additional concerns at a time when Iran needs to address the concerns of the international community," said Mike Hammer, spokesman for the U.S. National Security Council.

Sunday's announcement made clear that Iran does not consider uranium enrichment to be up for discussion at the talks beginning Monday in Geneva.

Salehi, head of the Atomic Energy Organization of Iran and the country's vice president, said Iran had for the first time delivered domestically mined raw uranium to a processing facility - allowing it to bypass U.N. sanctions prohibiting importation of the material.

Salehi said the uranium ore concentrate, known as yellowcake, was produced at the Gachin uranium mine in southern Iran.

Expectations for the talks had been low even before the announcement, with Iran saying it was prepared to discuss nuclear issues only in the context of global disarmament.

Officials from some of the six powers have said they would be pleased if the negotiations, the first in more than a year, yield even an agreement to meet at a later date to explore common themes.

The ultimate aim of the negotiating group - the United States, Russia, China, Britain, France, and Germany - is to commit Tehran to giving up uranium enrichment because of its potential use in making nuclear arms.

Tehran says it does not want atomic arms, but as it builds its capacity to potentially make such weapons, neither Israel, which feels particularly threatened by Iran's program, nor the United States has ruled out military action if the Islamic Republic fails to heed U.N. Security Council demands to freeze enrichment and other nuclear programs.

Ahead of the talks, expected to last two days, Western officials urged Tehran to address international concerns.

Invoking possible military confrontation over Iran's defiance, British Defense Secretary Liam Fox said Saturday: "We want a negotiated solution, not a military one - but Iran needs to work with us to achieve that outcome."

German Foreign Minister Guido Westerwelle said a nuclear-armed Iran was "unacceptable for us."