U.S.-Iran relations — Iran’s supreme leader seemed to put his authority behind Iran’s moderate new president Tuesday, calling for “heroic leniency” in navigating the country’s diplomatic dispute with the West.

The president, Hasan Rouhani, was elected in June on a moderate platform of ending the nuclear standoff with the West and increasing personal freedoms. In a speech to the Revolutionary Guards, considered stalwarts of the conservative wing of the government, the supreme leader, Ayatollah Ali Khamenei, said he was “not opposed to proper moves in diplomacy.”

In what may be a further signal that the Iranian leader’s victory in June elections has created a chance for intensified diplomacy, the country’s Foreign Ministry confirmed Tuesday that Rouhani had exchanged letters with President Barack Obama.

But asked about the tone of Obama’s letter — something the Iranians are extremely sensitive about — Marzieh Afkham, the ministry spokeswoman, said Iran expected improvement in the way Washington talked to Iran. “Unfortunately, the U.S. administration is still adopting the language of threat while dealing with Iran,” Afkham said at a weekly news conference. “We have announced that this needs to change into the language of respect.”

The U.S. and Iran have had no diplomatic relations since Washington ended ties after the seizure of 52 diplomatic personnel in 1979 after the Islamic revolution. Since his election, Rouhani has said he is interested in improving relations with the rest of the world, including the United States.

— New York Times News Service

TEHRAN, Iran — Iran’s new president, Hasan Rouhani, told Revolutionary Guard commanders this week that Iran would support whomever Syrians want as their leader even if it is not the country’s staunch ally, President Bashar Assad.

The statement appeared part of Rouhani’s diplomatic push to present himself as more conciliatory than his predecessor, Mahmoud Ahmadinejad, whose strident tone helped further isolate Iran. “Whoever Syrian citizens vote for to rule their country, we’ll agree with it,” Rouhani said, adding that the next election was scheduled for 2014.

But Rouhani’s statement came as a video surfaced online appearing to show Iranian commanders and Revolutionary Guards soldiers training and fighting alongside pro-government militias battling rebels trying to oust Assad.

Taken together, the speech and the video, if it is verified, point to the dual tracks employed by Iran as it tries to navigate the Syrian civil war and its widespread impact in the region. While calling for peace and diplomacy, Iran has also aided the government’s war effort.

Although Rouhani stressed Iran’s wish for a diplomatic solution in Syria, the United States has long said Iran was supporting Assad against the rebels.

The West, Turkey and several Persian Gulf countries openly support the rebels, providing arms, humanitarian aid and cash to at least keep the rebels strong enough to continue fighting, if not actually bolster the drive to oust Assad.

The video surfaced last week on a Dutch current affairs program. The show’s producer said it had been provided by rebels who said they had recovered it after the cameraman died in battle.

Restrictions on reporting in Syria prevent independent verification of the video’s provenance. There has been no official Iranian reaction to the footage.

In the video, men who appear to be Iranian commanders and soldiers are shown on patrol with Syrians, as well as engaged in firefights against rebels. The men speak in Persian with distinct regional accents.

One commander, who says he is speaking from a base near the northern city of Aleppo, boasts about his men’s accomplishments in Syria and is shown at the base giving orders to some Syrian soldiers.

Iran usually tries to remain in the background in conflicts, preferring to support local groups rather than sending its own soldiers into battle, but the United States has often accused Iran of sending troops to Afghanistan and Iraq. After 21⁄2 years of fighting, Assad’s military has begun to wear down, losing momentum and territory — prompting its allies in Iran, and Hezbollah in Lebanon, to provide more robust support.

With Iran’s help, Syria began to build up militias that took some of the pressure off the conventional forces.

During his speech to Guard commanders in Tehran this week, Rouhani praised the role of Iran’s Revolutionary Guards Corps in securing Iran’s interests in the region, though he did not address their having any active role in Syria. The West, Rouhani said, is executing a plan in the Middle East “to consolidate the power of Israel and weaken the resistance,” referring to its military and ideological alliance with Hezbollah and with Syria.

Syria is of great significance for Iran, he told the commanders. “We will not remain indifferent towards this critical issue.”

Rouhani said the West should realize that the Revolutionary Guards do not seek military dominance in the region. “Our discourse is the discourse of democracy, brotherhood and unity,” he said. “Our discourse is fighting with terrorism in the region.” Assad has long called the rebels fighting him terrorists.

In the footage released to the Dutch public broadcasting program by the Syrian rebel group, the Dawood brigade, one Iranian commander, who calls himself Haj Esmail, sits down for long, in-depth interviews with an unnamed videographer. He speaks of training Syrian militia members loyal to Assad in Tehran and criticizes the Syrian army for being too rigid with its fighters. “They want to come to our fronts because we show them respect,” he said.

“Syria is a war between Islam and nonbelievers,” Haj Esmail said in one of the interviews. “Good versus evil, our front is supported by Iranian fighters, Hezbollah and mujahedeen fighters from Iraq and Syria,” he said. “Our opponents are Israel, Saudi Arabia, Turkey, Qatar, funded by the Emirates, and Britain, France and the United States.”

Two Iranian analysts who watched the video said it appeared to be legitimate. They said the landscape did not appear to be in Iran and that the men’s accents and expressions marked them as Iranian. They said it was likely that the Guards would take videos of their exploits in Syria to document events.

“They are convinced Iran is winning in Syria and want to use the footage for later use,” said one analyst who asked to remain anonymous to avoid trouble with the Iranian government.

In his speech for the commanders, which was widely reported in the Iranian news media, Rouhani directly addressed the United States.

“You have come to the region uninvited, you leave and then you will see that the problems in the region will be resolved,” he said. “You will see that the region will turn into heaven. You should give up your power-seeking attitude. We have never interfered in the affairs of other countries and have no need to do so, and if we have something to shout for, we are shouting for democracy.”

Rouhani is scheduled to give a speech at the United Nations on Tuesday, which insiders say he will use to present a new, more moderate Iran. In recent weeks, Rouhani has stressed that he is ready for direct talks with the United States over Iran’s nuclear program.