The six-month period will give diplomats time to negotiate a more sweeping agreement.
The package includes freezing Iran's ability to enrich uranium at a maximum 5 percent level, which is well below the threshold for weapons-grade material and is aimed at easing Western concerns that Tehran could one day seek nuclear arms.
International monitors will oversee Iran's compliance.
For Iran, keeping the enrichment program active was a critical goal.
Iran's leaders view the country's ability to make nuclear fuel as a source of national pride and an essential part of nuclear self-sufficiency.