WASHINGTON - The White House expressed " grave concerns" Friday over Iran's nuclear program, saying there would be "consequences" if Iran fails to comply with requirements of the United Nations and the UN nuclear watchdog International Atomic Energy Agency (IAEA).
Gibbs said Iran has not taken advantage of opportunities to build trust and confidence, instead it has increased the international community's concerns about its nuclear program.
He said if Iran continues to fail to comply with the United Nations' and IAEA's requirements, "there will be consequences."
The spokesman said "the offer of constructive engagement is still on the table," calling Iran to return to negotiations with the five permanent members of the UN Security Council -- Britain, China, France, Russia, and the United States -- plus Germany.
Last month, the IAEA censured Iran for hiding an enrichment plant in Qom. Days later, Iran announced it would increase its enrichment program by building 10 new plants.
Earlier in the day, U.S. Secretary of State Hillary Clinton warned Latin American countries of promoting their ties with Iran, saying they should "think twice."
She said on another occasion the international community still wanted to engage with Iran, but were beginning to turn to more pressure, such as sanctions.
Iran maintains it has the right to generate nuclear energy for civilian purposes. But Western powers suspect Iran of attempting to build nuclear weapons.