The Iranian nuclear program is pushing U.S. 'patience,' and might be exhausted by the end of the year, a spokesman for the U.S. Department of State said.

"The President has said that our patience is not unlimited. He's indicated that we're willing to give a preponderance of attention to the engagement track until the end of the year, and if we don't get a positive response, we're going to start shifting our focus over to the other track, the track of pressure," Ian Kelly told a daily press briefing.

Iran's parliament demanded on Sunday that the government reduce cooperation with the International Atomic Energy Agency (IAEA) following Friday's resolution by the UN nuclear watchdog condemning Iran's work to build a new nuclear facility and censoring it for withholding information on its controversial nuclear program.

The Iranian lawmakers condemned the IAEA resolution and urged the government to quickly draft a plan to reduce cooperation with the UN nuclear watchdog.

Of the 35-member IAEA Board of Governors, 25 countries voted for the resolution, including Germany, Britain, China, France, Russia and the United States.