World powers meeting at the United Nations’ nuclear agency have agreed on a draft resolution sharply criticizing Iran for its nuclear activities while deferring any discussion of new U.N. sanctions until the spring, two Western diplomats familiar with the document said Thursday.

The resolution, which is expected to gain formal approval by the nuclear watchdog’s 35-nation governing board Friday, is a partial victory for Western powers seeking a unified message of rebuke to Iran over its nuclear policies.

But the omission of any specific recommendations for penalties was a concession to Russia and China, which have steadfastly opposed new sanctions against Iran, said the officials, who spoke on the condition of anonymity in describing diplomatic deliberations. Just 48 hours earlier, some Western governments had been skeptical that the two countries could be persuaded to support any resolution strongly critical of Iran.

The draft resolution expresses “deep and increasing concern about the unresolved issues” in Iran’s nuclear program, particularly allegations that Iran has sought sensitive technology used in making nuclear warheads, said a senior U.S. official familiar with the document now before board members of the International Atomic Energy Agency.

Although it contains no specific recommendation for new sanctions, the document urges Iran to agree to new negotiations “without preconditions,” and it calls on the IAEA to update its findings in March.

The wording sets the stage for a possible showdown in the spring if IAEA investigators find that Iran is continuing to violate its nuclear treaty obligations, a second Western diplomat said.

The Obama administration declined to comment on details of the draft resolution. “We are confident that there’s going to be a strong message coming out of the board of governors, and a unified message,” State Department spokesman Mark Toner said.

The latest round of diplomatic tussling over Iran stems from last week’s toughly worded IAEA report that documented what U.N. officials described as strong evidence of secret Iranian research on designing a nuclear warhead. The report suggested that Iranian scientists had been working methodically to gather technology for nuclear weapons until at least the end of 2003, and said some research appears to be continuing.

IAEA Director General Yukiya Amano, in remarks opening the two-day meeting in Vienna, said evidence gathered by the agency “indicates that Iran has carried out activities relevant to the development of a nuclear explosive device.”

Amano said he had written to Iranian nuclear officials proposing that a high-level IAEA delegation travel to Iran promptly to deal with issues raised in the report. Iran, which insists that its nuclear intentions are peaceful, dismissed the IAEA’s findings as “unbalanced, unprofessional and prepared with political motivation and under political pressure by mostly the United States.”

The Obama administration and key European allies have been seeking to use the new IAEA report to push for stronger U.N. sanctions against Iran, but Russia and China have publicly opposed such a move. Russian Foreign Minister Sergei Lavrov declared Monday that the “road of sanctions has been exhausted.”

Sergei Mikheyev, the head of Center for Current Policies, a Moscow think tank, said Russia’s consistent goal has been to “avoid armed conflict,” and it views sanctions as possibly opening the door for military intervention. But Moscow might be willing to accept “soft” measures in the hope that a compromise between Russia and the West would head off military strikes, he said.

Correspondent Andrew Higgins contributed to this report from Moscow.