U.S. President Barack Obama hailed as "concrete progress" the announcement that the pact finalized on Sunday between the 5+1 Group of nations and Iran will go into effect on Jan. 20, and he promised "modest relief" of the current sanctions on Tehran if the Iranians keep their commitments under the accord.

In a statement, Obama welcomed the "important step" announced Sunday by the top European Union diplomatic official, Catherine Ashton, regarding the date for the entry into force of the pact reached last November between Iran and the 5+1 Group, which includes the United States, France, the United Kingdom, China, Russia and Germany.

This is the "first time in a decade" that Iran has agreed to suspend work on its nuclear program, said Obama, adding that the agreement will help ensure that Iran does not build a nuclear weapon.

However, the president noted that additional diplomatic work will now begin on a broader, longer-term agreement, saying that "I have no illusions about how hard it will be to achieve this objective, but for the sake of our national security and the peace and security of the world, now is the time to give diplomacy a chance to succeed."

The pact signed in November obligates Iran to partially suspend its nuclear program in exchange for the lifting of certain sanctions and the commitment by the G5+1 not to impose new restrictive measures for a period of six months.

Despite the lifting of a limited number of sanctions on Iran, the United States will continue to "vigorously" enforce its overall sanctions regime and will not eliminate some of the most restrictive measures, Obama noted.

The president also said that if Iran fails to live up to its commitments, he will act to impose new sanctions, adding that he will veto any bills passed by the U.S. Congress to put additional sanctions in place on Iran while the agreement is in force.

Iran has denied any aspirations to build a nuclear weapon, claiming that its nuclear program is designed for peaceful purposes such as power generation and medical care.

The United States and Israel have refused to rule out the use of force against Tehran to prevent it from acquiring a nuclear weapon. EFE