As Iran and the United States appeared to be nearing an agreement to end hostilities this week, not everyone in Iran was on board.

The hard-line faction, a fringe but loud group with members in Parliament and a seat on the Supreme National Security Council, has openly opposed any concessions to Washington, using rallies, state media and private and public statements as tools to try to derail a deal.

It remains unclear when an actual agreement will be announced, if at all. President Trump met for two hours with cabinet members in the Situation Room at the White House on Friday, but he put off making a final decision, according to a senior administration official. Iran’s lead negotiator, Gen. Mohammad Bagher Ghalibaf, said in a social media post earlier in the day that Tehran did not trust Washington and that no step would “be taken before the other side acts first.”

But in Iran the political fight continues. State television, which is controlled by a hard-line director, has amplified the divisions in the country and portrayed negotiations as a failure. On Monday, President Masoud Pezeshkian scolded state television in a meeting with its senior leaders, calling on them to avoid sowing discord.

Mr. Pezeshkian said even Ayatollah Ali Khamenei, the former supreme leader killed on the first day of the war, “agreed that we must go to the negotiation table.”

“But now,” he continued, “we are advertising that we should not negotiate.”

At a packed rally of hard-line supporters in Tehran on Friday, large crowds waved flags and chanted for defiance. A state television reporter asked some attendees if Iran should retreat or continue fighting the United States and Israel. “We want them to punish them good,” one woman attendee said. “Stand firm, we are with you until our last drop of blood,” said one man.

“Trump must know that Iran, as the victor and conqueror of the field, sets the terms,” said Ebrahim Azizi, a conservative lawmaker and the head of Parliament’s national security and foreign policy committees, in a social media post on Friday.

Analysts close to the government in Iran say that the hard-line faction represents a minority view, both in the general public and among officials. Still, ignoring it risks alienating the part of the population that has been among the most loyal supporters of the Islamic Republic through political and social upheavals.

“This faction does not speak for the majority of Iranians and has been marginalized from key decision making; the nuclear talks are proceeding despite their disapproval,” said Mehdi Rahmati, a political analyst in Tehran, in a telephone interview. But, he added, “the system needs to come up with a plan to control them and keep them in check, otherwise they can become very dangerous for Iran’s stability.”

Even Iran’s new supreme leader, Ayatollah Mojtaba Khamenei, who is the son of the slain former leader, is not immune from their ire. On Thursday, a hard-line lawmaker cleric, Hamid Rasaee, took a jab at Ayatollah Khamenei in a social media post titled, “Who is worthy of the supreme leadership?” (Ayatollah Khamenei, who has been in hiding since the start of the war in late February, has expressed support for the nuclear negotiating team in written statements.)