Iran has dropped a demand to be allowed to continue some of its sensitive nuclear activities.
Iran says its nuclear intentions are peaceful
The UN's nuclear watchdog, the IAEA, said Tehran had sent a letter promising to include 20 centrifuges in a freeze on nuclear activities.
Tehran's demand to keep the centrifuges for research use had been threatening to derail a deal with EU countries.
A resolution on Iran endorsing the deal is expected to be adopted at an IAEA meeting in Vienna on Monday.
Centrifuges can be used to enrich uranium for use as fuel in power plants or weapons.
Iran's nuclear programme has sparked international concern.
Tehran denies US claims that it is developing banned weapons, saying its nuclear activities are peaceful.
The board of directors of the International Atomic Energy Agency (IAEA) is to discuss a draft resolution calling on Iran to "sustain the suspension" of uranium enrichment at nuclear facilities in Isfahan and Natanz.
It was held up when Iran demanded that some sensitive technology be exempted from its deal to freeze key parts of its nuclear programme.
The motion also proposes that IAEA Director General Mohamed ElBaradei should "report immediately" to the board if there was any evidence of incomplete suspension.
The BBC's Bethany Bell in Vienna says inclusion of the centrifuges in the freeze could save Iran from being referred to the UN Security Council, which could impose sanctions on Tehran
The US has led calls for the IAEA to refer Iran to the UN Security Council.
But any move towards sanctions is strongly opposed by China, which has the power of veto on the Security Council.
Some diplomats described Iran's demand as a bargaining chip in order to soften the terms of the resolution - a strategy which seems to have worked.
The draft IAEA resolution makes no mention of possible punitive action if Iran resumes enrichment.