(CNN) -- The United States and other countries are "getting close" to an interim deal with Iran that would prevent its nuclear program "from advancing, and roll it back" in key areas, a senior administration official said Friday.
Such a deal would "extend the breakout time" that Iran would need to achieve a nuclear weapon and "shorten the time to notice if they tried," the official told reporters on the condition of not being identified.
The proposed deal -- covering every aspect of Iran's nuclear program, including uranium enrichment, uranium stockpiles and all nuclear facilities including military ones -- would be completed during the next round of talks in Geneva, Switzerland, though difficult issues remain, the official said.
"We are going to work very hard next week, the official said. "I don't know if we'll reach an agreement. I think it is quite possible that we can. But there's still tough issues to negotiate."
The United States, along with the four other permanent members of the U.N. Security Council and Germany -- the so-called P5+1 -- came close to a deal during talks with Iran last week in Geneva, but the discussions ended with both sides blaming each other for the lack of an agreement.
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The P5+1 is "completely and totally unified" on the current outlines of the proposed deal, the official said.
The official warned against the imposition of further sanctions, which members of Congress have suggested.
"Further sanctions now threaten our good faith not just for Iran but for our P5+1 partners," the official said.
Under the plan, sanctions relief "way south" of one proposed figure of $10 billion would be "metered out over the six months of an interim agreement to ensure compliance."
Israel and the United States "may not see eye to eye on this tactically but are absolutely in agreement that Iran will not have a nuclear weapon," the official said.
News of the development came a day after President Barack Obama said additional sanctions targeting Iran's disputed nuclear program could undermine international progress already made on the issue.
"If we're serious about pursuing diplomacy, then there's no need for us to add new sanctions on top of the sanctions that are already very effective, and that brought them to the table in the first place," Obama told reporters Thursday at the White House.
He said he would like to see if a "short-term, phase-one deal" with Iran can be put in place in the near term that requires Tehran to freeze aspects of its nuclear program while the international community negotiates a more comprehensive long-term deal.
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His remarks came amid a growing call in Congress for tighter sanctions to get Iran to agree to a deal that would stop what U.S. officials have said is its march toward a nuclear weapon.
"If it turns out six months from now that they're not serious" about the agreement, "we can dial those sanctions right back up," Obama said, noting that the economic penalties have hurt Iran's economy.
Obama's comments came the same day the International Atomic Energy Agency, the U.N. nuclear watchdog, released a report saying Iran had halted the expansion of a majority of its uranium enrichment capacity.
Undersecretary of State Wendy Sherman is scheduled to lead the American delegation at the round of talks next week in Geneva.