United Nations Secretary-General Ban Ki-moon has defended his controversial visit to Iran, saying that he had used this week's trip to push hard for human rights and transparency from Tehran over its nuclear programme.

"I believe in the power of diplomacy and I believe in dialogues and I believe in engagement. This is exactly what I did during my visit to Tehran," Ban told Reuters on a stopover in Dubai before flying back to U.N. headquarters in New York.

While conceding he had not always been satisfied with the responses of Iranian leaders he spoke to this week, he rejected accusations by the US and Israel that he had been playing into Tehran's hands by attending an international summit which Iran used to raise its diplomatic profile.

"I think that it should not have been controversial," he said. "As a secretary-general of the United Nations, I have a mandate to engage with all the member states of the United Nations."

Making the first visit by a U.N. chief to Iran since his predecessor travelled there six years ago, Ban attended the summit of the Non-Aligned Movement, a group of 120 mostly developing nations. Among these were senior ministers from Syria's embattled government who, he said, agreed to consider his request for greater access for international aid workers.

Isolated by international economic sanctions imposed over its nuclear programme, and unpopular among many states for its support of President Bashar al-Assad in Syria's civil war, Iran used the NAM summit to present an image of diplomatic power - to its own people, as well as the rest of the world.

Before the summit, Washington made clear that it wanted Ban to boycott the event. "Iran is going to manipulate this opportunity and the attendees to try to deflect attention from its own failings," a State Department spokeswoman said.

Israeli Prime Minister Benjamin Netanyahu also urged Ban to cancel, calling his trip a "big mistake", Israeli media said. Netanyahu sees Iran, and a nuclear programme which Tehran insists is for civilian use, as a threat to Israel's existence.

Criticism

Ban appeared to go out of his way in Tehran to avoid being seen as endorsing Iranian policies. On Thursday, he discomfited his hosts by publicly denouncing as "outrageous" Iranian threats against Israel and claims that the Holocaust never took place.

In public comments later, he urged the Iranian leadership to release opposition leaders and political activists to create the conditions for free expression and open debate.

Ban's criticism may have had little effect on public opinion within the country, however. Local media reported his comments selectively, focusing on references to Iran's importance in the world and generally omitting critical remarks.

However, Ban said on Friday that he had also used meetings with Iran's Supreme Leader Ayatollah Ali Khamenei and President Mahmoud Ahmadinejad to push for change in the country: "I made a very strong push on the nuclear issues and when it came to human rights issues, again I made it quite clear," he said.

Ban said he had told Iranian leaders that they had a responsibility to do more to assure the world that their nuclear programme was for solely peaceful purposes. The leaders' responses were not always satisfactory, he added.

"In some questions they were trying to explain their positions, particularly when it comes to nuclear issues," he said. "They were not giving me any concrete answers."

On human rights, Ban said he pressed Iran to permit more freedom of expression, strengthen women's rights and move toward democracy. He said he had brought up some specific human rights cases: "I expect some positive actions may be taken," Ban said without elaborating.

He also visited Tehran's School of International Relations to discuss with teachers and students what the country should do "if the Iranian government really wants to have a full integration into the international community, as a responsible member of the United Nations".

While there he urged the authorities to release opposition leaders and political activists to create the conditions for free expression and open debate ahead of next year's presidential election.

Mirhossein Mousavi and Mehdi Karoubi have been held incommunicado since February last year. The two leaders -- who alleged the 2009 re-election of Mahmoud Ahmadinejad was rigged -- had called for a rally in support of uprisings in the Arab world.

Ban said he used the Tehran summit to lobby others governments which attended to support Algerian diplomat Lakhdar Brahimi, who is due this Saturday to replace Kofi Annan as the U.N.-Arab League mediator trying to end the war in Syria.

He asked Syrian Prime Minister Wael al-Halki and Foreign Minister Walid al-Moualem, also attending the summit, to allow international aid workers more access in order to ease a humanitarian crisis affecting hundreds of thousands: "They told me they would consider this matter favourably," Ban said. – Reuters