TEHRAN — Iran’s supreme leader said on Wednesday that he did not believe that all sanctions against his country would be lifted, a move he had previously said was an essential condition for nuclear talks to succeed.

The supreme leader, Ayatollah Ali Khamenei, who has the final say in Iran on any nuclear agreement between his country and world powers, and who has commented regularly on the negotiations, has stressed that he is not optimistic about whether a compromise can be reached. But in a speech on Wednesday, referring to the United States, he said he did not believe that sanctions would be lifted “even if the talks continue on the basis of what they dictate.”

In January, Ayatollah Khamenei called Iran’s opponents in the talks “greedy” and emphasized that sanctions must “really be lifted” for any agreement to be accepted by the Islamic republic. If not, he said, Iran would challenge the sanctions by further developing its own economy, which has suffered from isolation and mismanagement.