Iran's interim nuclear deal with six major powers will come into force on January 20, the Iranian Foreign Ministry and the European Union said on Sunday.
"Capitals have confirmed the result of the talks in Geneva ... the Geneva deal will be implemented from January 20," Marzieh Afkham, spokeswoman for the Iranian Foreign Ministry, told reporters in Tehran, the semi-official Mehr news agency said.
EU foreign policy chief Catherine Ashton also confirmed the date, and said the sides would now ask the United Nations' nuclear watchdog to verify the deal's implementation.
"We will ask the IAEA to undertake the necessary nuclear-related monitoring and verification activities," she said in a statement.
Ashton represents the six powers - the United States, Russia, China, France, Britain and Germany - in contacts with Iran related to its controversial nuclear program.
Senior officials from the European Union and Iran met in Geneva on Thursday and Friday to iron out remaining practical questions related to the implementation of the November 24 deal, under which Iran agreed to curb its most sensitive nuclear work in return for some relief from Western economic sanctions.
EU spokesman Michael Mann said on Friday that any agreements would need to be validated by the governments of Iran and the six powers.
The accord is designed to last six months and the parties hope to use the time to negotiate a final, broad settlement governing the scope of Iran's nuclear program.
In response to the confirmation, Obama repeated that "I will veto any legislation enacting new sanctions during the negotiation" of a long-term agreement with Iran. He also added that the US would give "modest relief" on sanctions as Iran fulfills its commitment to the deal, and that the US "will move to increase our sanctions" if Iran does not follow through.
Obama said the deal was the "first time in a decade" Iran had agreed to halt progress on its nuclear program and said the agreement will help prevent Iran from building a nuclear weapon.
"With today's agreement, we have made concrete progress," Obama said in a statement, noting work now begins on the broader, long-term agreement.
"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," he said.
But Obama also faces pressure from the US Congress to pass new sanctions on Iran as a type of "insurance policy" to push Tehran to abide by the new deal.
Fifty-nine senators - 16 of them Democrats - of the 100 in the chamber have signed on to a bill that would require further cuts in Iran's oil exports.
Obama said on Sunday he would veto the bill if Congress passes it, but said the United States would be ready to increase its sanctions if Iran fails to comply with the terms of the six-month deal.
"Imposing additional sanctions now will only risk derailing our efforts to resolve this issue peacefully, and I will veto any legislation enacting new sanctions during the negotiation," Obama said in the statement.
Western powers suspect Iran has been trying to develop the ability to manufacture a nuclear weapon. Iran says its program is aimed purely at civilian electricity generation and other civilian purposes.