By Yeganeh Torbati
DUBAI (Reuters) - Iranian Supreme Leader Ayatollah Ali Khamenei said on Saturday he supported moderate President Hassan Rouhani's diplomatic opening to the United States at the U.N. General Assembly last week but some aspects of it were "not proper".
Khamenei did not elaborate on his objections but also said he did not trust the United States as a negotiating partner, hinting at disapproval over an historic phone conversation between Rouhani and U.S. President Barack Obama.
But despite its reservations, Khamenei's overall endorsement will probably protect Rouhani against conservative hardliners opposed to his pursuit of "constructive interaction" with the world to ease Iran's economically crippling isolation.
Khamenei - the ultimate arbiter of high state policy under Iran's unwieldy dual system of clerical and republican rule - said prior to Rouhani's trip that he supported "heroic flexibility" in diplomacy, while cautioning that the Islamic Republic must always remember who its foes are.
The Rouhani-Obama phone chat, the first between presidents of the two deeply estranged countries since Iran's 1979 Islamic Revolution, capped a week of overtures by Rouhani and his foreign minister, Mohammad Javad Zarif, to the West.
The landslide election in June of Rouhani has raised hopes of a negotiated settlement to Iran's long-running dispute with world powers over its nuclear program - though it is Khamenei who will make the final decision on the contours of any deal.
"We support the government's diplomatic movement, including the trip to New York, because we trust the government and we are optimistic regarding it," Khamenei said in a speech quoted by ISNA news agency.
"But some of what happened in New York was not proper, because the U.S. government is not trustworthy, is self-important and illogical, and breaks promises," he said.
Rouhani also won a resounding endorsement for his conciliatory moves at the U.N. General Assembly from the Iranian parliament, a significant gesture because the hardline assembly is dominated by factions loyal to Khamenei.
The president and his team are hoping to secure a removal of international sanctions on Iran's banking, energy, and shipping sector that slashed vital oil exports and hobbled the economy.
The sanctions were imposed over Iran's failure to address suspicions that it is enriching uranium to develop a nuclear arms capability. Iran says it wants only civilian atomic energy.
The next round of talks between Iran and six world powers on the nuclear stand-off, which has raised fears of a new Middle East war, is to be held in Geneva on October 15-16.
A diplomat based in Tehran said Khamenei's carefully calibrated comments looked like an effort to play down expectations from negotiations in the near future.
"There have already been skeptical signs and in a way these comments are not that surprising," the diplomat said, speaking on condition of anonymity. "The distance between Iran and the United States is very wide. It can't just turn into smiles and friendliness. He (Khamenei) is giving it a chance, but if it doesn't work he'll go back to his own way."
While in New York, Rouhani emphasized a changed atmosphere between Iran and the United States, and said his goal is to solve problems and pursue "the shared interest between the two nations.
But while Rouhani's attempts to undo some of his predecessor Mahmoud Ahmadinejad's bellicose rhetoric on the world stage have met with cautious approval at home from conservatives, some hardliners in Iran's complex power structure have been critical given their hostility to any thaw with the United States.
Upon Rouhani's return to Tehran last week, he was greeted at the airport by a large crowd of supporters and a smaller group of protesters who threw eggs and shoes at his official car.
And the commander of Iran's Islamic Revolutionary Guard Corps, a pillar of the political establishment, declared last week that Rouhani's phone call with Obama was premature.
Both Rouhani and Obama face domestic resistance to rapprochement from those who fear their president may be too inclined to grant concessions before the other side takes any concrete steps. This wall of mistrust has impeded negotiations.
In one indication of the roadblocks to rebuilding relations severed since 1980, Zarif said on CNN he was "disappointed" with Obama for a statement he made in Washington this week after meeting with Israeli Prime Minister Benjamin Netanyahu.
Israel has threatened to attack Iran unless it ends its nuclear program and Obama said that Washington would "take no options off the table, including military options," to prevent Iran getting a nuclear weapon.
That sort of language was "insulting to the Iranian people," Zarif told CNN in an interview. "You do not deal with another state with mutual respect by threatening them, by trying to intimidate them...The Iranian people react very, very negatively to such languages of threat and intimidation."
(Additional reporting by Marcus George in Dubai; Editing by Mark Heinrich)