Though he described sanctions as a "grievous violation of human rights" that "affect the weak" and "do not solve problems," Mr. ElBaradei said Iran's continued intransigence regarding its nuclear program would likely lead world powers to increase their pressure on Iran.
Mr. ElBaradei, who is set to retire from the agency at the end of November, said he still hoped Iran's leadership would accept a plan to address concerns about its nuclear activities but acknowledged that it was "a fleeting opportunity."
He urged the international community to continue to engage with Iran, saying that "small steps and negotiations" are necessary to achieve results.
"We can threaten to use force, but this is a bridge to nowhere," Mr. ElBaradei said.
Diplomats familiar with the talks say Western powers will wait until the end of the year for Tehran to accept a deal brokered with Iran this fall that would require the country to ship some of its uranium stockpile abroad for reprocessing into fuel for a medical-research reactor.
Mr. ElBaradei's remarks came as top officials from the five permanent members of the United Nations Security Council -- the U.S., U.K., France, Russia and China -- plus Germany, met in Brussels to discuss the standoff with Iran.
The group issued a statement expressing disappointment that Iran had failed to respond to proposals aimed at calming worries about its nuclear ambitions. They urged Iran "to engage seriously with us in dialogue and negotiations."
The six said they viewed Iran's failure to notify the IAEA about the existence of an underground uranium enrichment facility near the holy city of Qom as a breach of Iran's safeguards agreement with the agency and "in defiance of several UN resolutions."
The officials said they would meet again soon to decide about next steps.
International criticism of Iran's nuclear program escalated in September after the existence of the Qom facility came to light. President Obama has said the facility appears to be designed to produce fuel for a secret military program.
Mr. Obama has called for a two-track policy of negotiations backed by the possibility of sanctions, should the talks fail to lead to an agreement that would restore confidence in the peaceful nature of Iran's nuclear program.
At the U.N. Friday, Iran drew criticism for how it handled the aftermath of the country's disputed presidential election. The General Assembly's human-rights committee passed a resolution condemning Tehran's violent response to protests against the results of the June balloting as "serious ongoing and recurring human-rights violations."
Mohammad Khazaee, Iran's ambassador to the U.N., called the Canadian-sponsored resolution "politically charged and motivated."