AT HIS first news conference since taking office, Iran’s new president, Hassan Rouhani, declared his willingness to negotiate with the United States. Speaking on Tuesday, he insisted he is ready to enter “serious and substantive” talks about Iran’s disputed nuclear program and said a solution can be reached only through “talks, not threats.”He added, “If the United States shows goodwill and mutual respect, the way for interaction will be open.”

These are only words, and whether there is any meaning behind them is not clear. It does seem that after eight years of the fiery Mahmoud Ahmadinejad as president, Mr. Rouhani is attempting to change the tone. He is not a reformer, but he is a centrist, and his election victory, as well as his early statements, could signal a new course, somewhat different from the bitter confrontations of recent years. Mr. Rouhani defeated a slate of more conservative candidates. He has talked of expanding civil liberties and freeing some political prisoners. He has appointed some technocrats to his cabinet and has suggested he may lift or ease Internet censorship, which has been heavy and heavy-handed. “Gone are the days when a wall could be built around the country,” he said, according to the Economist. “Today there are no more walls.”

All well and good. But the United States and its partners who want Iran to stop enriching uranium for a potential nuclear weapons program can ill afford to see Mr. Rouhani through rose-colored glasses. The Supreme leader, Ayatollah Ali Khamenei, remains the true center of power and controls Iran’s nuclear program. The Revolutionary Guard Corps is still a major force, up to its eyeballs in Syria and supplying Hezbollah. Mr. Rouhani, an experienced operator in Iran’s elite jockeying, will have all of them breathing down his neck in the months ahead.

Nonetheless, the West should resume negotiations soon to explore the depth of Mr. Rouhani’s seriousness and whether his election has come with room to maneuver. The White House reacted positively to the new president’s overtures, and the European Union’s senior foreign policy official, Catherine Ashton, called on Mr. Rouhani to agree to a new round of talks as soon as possible.

Mr. Rouhani’s priorities may well be at home, where Iran’s economy is crumbling. He will undoubtedly be eager to ease strict international sanctions, yet it is not clear whether or how quickly he can or wants to change course on Iran’s nuclear program. The Western powers should swallow hard and show up ready to talk. Mr. Rouhani’s demand for mutual respect is not unreasonable.

Those talks must proceed with urgency, however. As Israeli Prime Minister Benjamin Netanyahu warned Wednesday, “while everybody is busy talking to him, he’ll be busy enriching uranium.” Mr. Netanyahu, in fact, claimed that the Iranian nuclear program has accelerated. At about the same time, the publication IHS Jane’s Defence Weekly revealed the previously undisclosed location of a new Iranian facility that could be used to launch intercontinental ballistic missiles. Certainly international sanctions must remain in place absent genuine evidence that Iran has abandoned its nuclear weapons ambitions. No amount of sweet talk can change that.