WASHINGTON — Iran’s supreme leader, Ayatollah Ali Khamenei, rejected any idea of bilateral talks with the United States on Thursday, in a speech in which he seemed to dismiss the views of Iranian officials — including the country’s foreign minister — who had advocated for such negotiations.

“The Iranian nation will not negotiate under pressure,” Ayatollah Khamenei said. Noting the international sanctions against Iran, which were bolstered on Wednesday by new American financial restrictions that essentially reduce Iran to using its oil for barter trade, he added: “The U.S. is pointing a gun at Iran and wants us to talk to them. The Iranian nation will not be intimidated by these actions.”

“Direct talks will not solve any problems,” he concluded.

His statement was considered particularly important because, as one senior Obama administration official put it, “we believe Khamenei now holds the entire nuclear file.”

But the White House did not immediately react to the statement, and some officials said that history — including during the Iran-Iraq war — demonstrates that Iran can change its position quickly. Despite the ayatollah’s comments, it appears that talks scheduled to begin Feb. 26 between Iran and six nations, including the United States, will go ahead in Kazakhstan.