Ayatollah Ali Khamenei, Iran’s supreme leader, said negotiating with the United States was “unwise, unintelligent, and not honorable,” just days after President Trump said he was willing to revive negotiations with Tehran.

But Mr. Khamenei stopped short of ordering Iran’s government, which for months has sent signals that it is interested in negotiations, not to engage with Washington. And though Mr. Khamenei made an unusual gesture last year of openness to talks, he has generally taken a publicly hostile posture toward Washington even while quietly allowing Iranian officials to negotiate.

In comments on Friday, Mr. Khamenei argued that Iran’s previous experiences negotiating with the United States showed that Washington could easily renege on agreements. Under Mr. Trump’s previous administration, the United States unilaterally withdrew from a nuclear deal under which Iran would limit its enrichment and stockpiling of uranium in exchange for sanctions relief.

“Negotiating with America will solve no problem. The proof? Experience,” Mr. Khamenei said, according to Iran’s state news agency, IRNA, which said his comments came during a meeting with commanders and staff from the Iranian armed forces.

“The very same person who is now in office tore up the agreement,” Mr. Khamenei said. “One shall not negotiate with a government like this. Negotiating is unwise, unintelligent, not honorable.”

Ali Vaez, the Iran project director for the International Crisis Group, said on social media that the comments could simply be “in line” with Mr. Khamenei’s previous public approach. In 2011, he had publicly opposed negotiations with the Obama administration, even as he authorized negotiators to meet secretly with U.S. officials in Oman.