TEHRAN — With exactly a week left before the deadline for a final agreement to limit Iran’s nuclear program, the country’s supreme leader appeared to undercut several of the central agreements his negotiators have already reached with the West.

In a speech broadcast live on Iran state television, the supreme leader, Ayatollah Ali Khamenei, demanded that most sanctions be lifted before Tehran has dismantled part of its nuclear infrastructure and before international inspectors verify that the country is beginning to meet its commitments. He also ruled out any freeze on Iran’s sensitive nuclear enrichment for as long as a decade, as a preliminary understanding announced in April stipulates, and he repeated his refusal to allow inspections of Iranian military sites.

American officials said they would not be baited into a public debate with the ayatollah, who has the final word on nuclear matters. But with Western foreign ministers already hinting that the negotiations may go past the June 30 deadline, both American and European officials have said in recent weeks that they are increasingly concerned about the possible effects of the ayatollah’s statements.

Even if the remarks were made chiefly to mollify hard-liners and military leaders, they say, they could sharply limit the flexibility of Iran’s chief negotiator, Foreign Minister Mohammad Javad Zarif, as he heads into the week when the most difficult concessions are likely on both sides.