Iran announced on Thursday it had responded to a letter from President Trump in which the American president had urged direct negotiations with the government in Tehran on a deal to curb the country’s advancing nuclear program.

Iran appeared to be taking the middle ground, neither rejecting negotiations with the United States nor accepting face-to-face talks with Mr. Trump.

But Kamal Kharazi, the top foreign policy adviser to Iran’s supreme leader, Ayatollah Ali Khamenei, said, according to local news reports, “The Islamic Republic has not closed all the doors and is willing to begin indirect negotiations with the United States.”

The countries have not had official diplomatic relations since the Islamic Revolution in 1979, but they have engaged directly and indirectly on issues like the nuclear program, detainee swaps and regional tensions.

Iran said it submitted its written reply to Mr. Trump through Oman on Wednesday. The foreign minister of Iran, Abbas Araghchi, said Tehran had presented a comprehensive view on the issues raised by Mr. Trump and on the overall situation in the Middle East, according to the official news agency IRNA.

“Our policy is to not negotiate directly while there is maximum pressure policy and threats of military strikes,” Mr. Araghchi said on Thursday. “But indirect negotiations can take place as they have in the past.”

What did the Trump letter say?

Mr. Trump sent the letter this month to Mr. Khamenei, saying he preferred diplomacy to military action.

“I’ve written them a letter saying, ‘I hope you’re going to negotiate, because if we have to go in militarily, it’s going to be a terrible thing,’” Mr. Trump told Fox News. “You can’t let them have a nuclear weapon.”

On March 12, Anwar Gargash, a senior diplomat from the United Arab Emirates who traveled to Tehran to deliver Mr. Trump’s letter, told Iranian news media that it contained “threats” and also an opportunity.

Steve Witkoff, the Trump administration’s special envoy to the Middle East, revealed more details in an interview with Tucker Carlson, a former Fox News host who is now a popular podcaster. Mr. Witkoff said the letter roughly said: “We should talk, we should clear up the misconceptions, we should create a verification program so that nobody worries about weaponization of your nuclear material.”

An Iranian official who asked not to be named because he was not authorized to speak publicly said that Mr. Trump had set a two-month deadline for Iran to negotiate, a detail initially reported by Axios.

Sanam Vakil, director of the Middle East and North Africa program at Chatham House, a research institute based in London, said the letter-writing between Tehran and Washington showed that both sides were “sizing each other up and finding different channels, some public and many private, to define what they can achieve.”

“This is an opportunity for both sides,” she added, “but it comes with a thousand risks and challenges.”

What is the view in Iran?

Since Mr. Trump’s election, officials and pundits in Iran have publicly debated the topic, with a conservative hard-line faction vehemently objecting to talks or concessions and a moderate and reformist faction arguing that negotiations are necessary to lift sanctions.

Mr. Khamenei, who has the last word on all key state matters, has said he does not believe that Iran would gain from talks.

President Masoud Pezeshkian, a moderate, has distanced himself from that view, telling Parliament this month that he favored negotiations but would follow Mr. Khamenei’s directive.

On Thursday, Mr. Khamenei’s office signaled a shift in tone, based on Mr. Kharazi’s remarks.

What other options are being considered?

If talks on a deal to curb Iran’s nuclear program fail, Israel and the United States have suggested the possibility of launching targeted strikes on the two main underground nuclear facilities in Iran, Natanz and Fordow.

But that risks setting off a wider regional war since Iran has warned it would respond to any strikes on its soil. And any attacks could destabilize the Middle East, with Tehran turning to its network of weakened but still active proxy militias, like Hezbollah in Lebanon and the Houthis in Yemen.

Iran maintains that its nuclear program is for peaceful purposes, but the West and Israel are concerned that Tehran has been secretly planning a faster, cruder approach to building a weapon.

In 2018, Mr. Trump pulled the United States out of the 2015 nuclear deal with Iran and imposed tough economic sanctions. The moves prompted Iran to abandon its commitments to the deal and increase uranium enrichment from a cap of 3.5 percent to 60 percent now.

The United Nation’s nuclear watchdog says in its latest report that Iran has stockpiled enough enriched uranium to make several bombs. But the watchdog says it has found no evidence that Iran is weaponizing its program.

“Iran is at a crossroad, between having an off ramp or being militarily hit,” said Ms. Vakil, of Chatham House. “It’s a year of really consequential decisions, and how they play their hand could give them a lifeline or lead to further strikes and weakening of the government.”