Washington, April 9 (EFE) .- United States today expressed skepticism about the progress made by Iran on its nuclear program and urged Tehran to comply with its obligations international and suspend uranium enrichment and related activities.

The Iranian president, Mahmoud Ahmadinejad, announced on Thursday that his country has achieved two important advances in the technology of enriching uranium, the fuel storage and evidence of two new models for more powerful centrifuges in Natanz plant.

The spokesman's office in the State Department, Robert Wood, made again today in his daily press conference, call on Iran to comply with its obligations.

We have asked Iran to suspend uranium enrichment and related activities with it. We want to see happen. This is not only an appeal from U.S. but from other countries. And we remain concerned about what Iran is doing, he said.

The suspension of Iranian uranium enrichment is a fundamental requirement of the international community to believe that what Iran is pursuing a nuclear program is peaceful, he said.

Iran also announced it is currently installed 7000 centrifuges at Natanz.

We do not know what to believe. We have heard so many claims and assessments over the past few years, said Secretary of State Hillary Clinton after the ministerial meeting held in conjunction with the Secretary of Defense Robert Gates , with its Australian counterpart, Stephen Smith and Joel Fitzgibbon, respectively.

It is not clear, so it is clear that Iran has obligations to fulfill needed. And we will continue reaching out to Iran with the twin-track strategy. We have a package of incentives on the table that we believe is good. Iran has to accept it and use it, said Wood.

The G-5 1 (the five permanent members of the Security Council, U.S., United Kingdom, France, Russia and China) plus Germany offered to Tehran last year a package of incentives to abandon uranium enrichment.

Wood recalled that Washington has offered a dialogue with Iran without preconditions, which, however, does not imply that the country does not have to meet their obligations, he said.

The Government of U.S. said yesterday that from now on participate as a full member of the nuclear talks in Group 5, 1 which represents a turn in Washington's strategy to address this issue compared to the previous Executive, under which participated as an observer rather in negotiations.

Clinton noted that one of the reasons for the U.S. participate in nuclear talks is to insist on Iran's international obligations.

And to ensure that the International Atomic Energy Agency (IAEA) is the only credible source of information because there is a big difference between the estimates of this organization and those of Iran.

Ahmedineyad said at the inauguration of the plant Isafahan, culminating in the production chain Iranian nuclear power, that his country is willing to talk with others if it is a fair and equal dialogue.

Wood said it was too early to talk of a possible meeting between Clinton and Iranian authorities.