TEHRAN — For more than a year, Iran’s president, Hassan Rouhani, had been walking a political tightrope by trying to restore some level of relations with the country’s archenemy, the United States. His hard-line opponents pelted him with eggs for his efforts, while those who voted for him hoped for a possible thaw.

In one of his most famous breaks with the past, Mr. Rouhani — nicknamed the “diplomatic sheikh” here because of his skills in dealing with foreigners — even held a phone call with President Obama early in his term. Since then he has publicly pleaded to explore open discussions and at least some cooperation with the United States.
But on Saturday Mr. Rouhani struck a starkly different tone. In a news conference that marked his being in office more than a year, Mr. Rouhani echoed the longstanding Iranian view that the United States can never be trusted. Not only did he rule out any cooperation on fighting regional terrorist groups (after suggesting the idea himself last month), he also hinted that American actions were responsible for creating the Islamic State in Iraq and Syria, as well as Al Qaeda and the Taliban, a mantra offered by the Iranian leadership.

In addition, he expressed doubt about whether the United States had “adequate good will” to resolve the nuclear issue, and called new sanctions by the Obama administration over the nuclear program “a very ugly move."

In the complicated world of Iranian politics, it is difficult to know if Mr. Rouhani’s statements — his toughest on the United States since taking office — represent a shift in his thinking or are tailored to a domestic audience where hard-liners have increasingly worked against his pursuit of domestic freedoms and better foreign relations.

It is also possible the speech was a tactical move to strengthen Iran’s position before renewed talks on Iran’s nuclear program, which it says is for peaceful purposes but the West suspects is aimed at building an arsenal of bombs.

Mr. Rouhani’s statements came just a day after the Obama administration imposed the new sanctions, blacklisting 30 people and entities it said are linked to the country’s nuclear program.

In a statement, the White House said the sanctions were a continuation of its strategy to crack down on groups suspected of seeking to avoid or violate existing sanctions, even as “the United States remains committed” to reaching an accord by late November.

But the latest sanctions appeared to frustrate Mr. Rouhani.

“Yes, of course, we bypass the sanctions,” he said during his news conference. “We believe they are illegal and crimes against humanity.”

He added that for relations to improve, the United States must make the first move.

“Our people distrust Americans,” he said. “It would be better if Americans could do something that could help to build some trust in the future. Unfortunately, their moves only deepen distrust.”

Although he was one of the political stars of the United Nations General Assembly meeting last year, hobnobbing with international leaders who had long shunned Iran, he said Saturday that he had not decided whether he would make the trip this year to the headquarters in New York. “And,” he said, “I have no plans to meet with Mr. Obama.”

The phone call between the two men came just after his appearance at last year’s United Nations session, and helped lead to a temporary nuclear agreement in November, under which some parts of Iran’s nuclear program were suspended, along with some sanctions against Iran.

Although the country’s supreme leader, Ayatollah Ali Khamenei, has allowed Mr. Rouhani to pursue the diplomacy, he also stepped up his criticism of the United States in recent months and said he is pessimistic that the nuclear talks and direct talks with the United States will lead to anything.

Some analysts said Mr. Rouhani’s angry tone Saturday might be aimed at pre-empting criticism from influential hard-liners who may be waiting for the right moment to attack the government. Already some hard-liners are calling for an end to the talks because of the new sanctions.

Even some of his most optimistic supporters are beginning to say there will be no thaw in relations any time soon. “At least the nuclear talks will continue,” said Mojgan Faraji, a journalist for pro-Rouhani media. “But relations between Iran and America seem almost impossible now.”

Developments in the region have suggested the United States and Iran have increasingly parallel interests, with both countries seeing the newly powerful Islamic State in Iraq and Syria as a potent threat after it gobbled up territory in Iraq and Syria. The Sunni extremist group is opposed to Iran, which is overwhelmingly Shiite.

Iran has supported the Iraqi Kurds in their struggle against the group, and played an important role in persuading Prime Minister Nuri Kamal al-Maliki of Iraq to give up his bid for a third term, a move the United States supported.

“Still, we are not Germany or Turkey, who can work with the U.S.,” said Saeed Laylaz, an economist and government adviser. “In the end we do not have any normal relations with each other.”

Hard-liners said Saturday they feel vindicated by Mr. Rouhani’s statements.

“President Rouhani was realistic today; finally he realized that our supreme leader has been right all the time in his pessimism over the U.S. intentions,” said Hamid Reza Taraghi, a hard-line political analyst with good connections in the office of Ayatollah Khamenei. “Today it is clear that there is only one voice in Iran, and that is the voice of Mr. Khamenei.”