President Trump said on Thursday that his administration was nearing a nuclear deal with Iran, one of the key objectives of his second term.

“We’re in very serious negotiations with Iran for long-term peace,” Mr. Trump said at a business round table in Doha, Qatar, on the third day of a four-nation tour of the Middle East. “And if we do that, it’ll be fantastic.”

“Iran has sort of agreed to the terms” he said, according to a White House pool report. “We’re getting close to maybe doing a deal.”

Exactly what that deal, and its terms, would look like remained unclear. Both sides are far from a consensus on key issues. A major sticking point is whether, under a new deal, Iran would be able to enrich uranium at a lower grade for civilian use or would have to dismantle its program completely, as the Trump administration has, at times, demanded.

Mr. Trump said he wanted Iran to become a great country, but “they can’t have a nuclear weapon.”

Iran’s foreign minister, Abbas Araghchi, said on Thursday at a book-signing ceremony in Tehran for his new book, “Power of Negotiations,” that Iran would never give up its right to civilian nuclear energy, adding that “none of our nuclear enrichment facilities will be dismantled.”

Mr. Araghchi and Steve Witkoff, the president’s special envoy, have held four rounds of negotiations, mediated by Oman, which both sides have described as constructive.