PARIS — Iran and six world powers have agreed on how to put in place an accord that would temporarily freeze much of Iran’s nuclear program, American and Iranian officials said on Sunday.

That accord would go into effect on Jan. 20.

International negotiators worked out an agreement in November to constrain much of Iran’s program for six months so that diplomats would have time to pursue a more comprehensive follow-up accord.

But before the temporary agreement could take effect, negotiators had to work out the technical procedures for carrying it out and resolve some of its ambiguities in concert with the International Atomic Energy Agency.

Under the interim agreement, Iran would stop enriching uranium beyond 5 percent, a level that would be sufficient for energy production but that would require further enrichment for making bombs.

Iran’s stockpile of uranium enriched to 20 percent would be diluted or converted to oxide so that it could not be readily used for military purposes.

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