In a speech delivered in Istanbul, Ban said the agreement Iran had reached on Monday with Turkey and Brazil, both non-permanent members of the UN Security Council, was "an important initiative in resolving international tensions over Iran's nuclear program by peaceful means. "I have mentioned Turkey's welcome role with respect to Iran, working with Brazil. We hope that this and other initiatives may open the door to a negotiated settlement," Ban said.

But he added that the International Atomic Energy Agency, which brokered the basis of the deal last October only to see it unravel when Iran raised numerous objections, would provide its own professional assessment.

The United States handed the UN Security Council a draft resolution on Tuesday that would expand UN sanctions, hitting Iran's banking and other industries over Iran's protracted refusal to suspend uranium enrichment.

The draft resolution was agreed by all five permanent Security Council members after months of negotiation.

Iran dismissed it as lacking legitimacy but US President Barack Obama has insisted Washington will press ahead and that Tehran cannot be trusted.

The Islamic Republic denies Western suspicions that its secretive atomic energy program is aimed at developing nuclear weapons capability and has said it will continue enriching uranium for fuel for electricity generation.
 

Ban's spokesman had said on Monday the nuclear fuel talks shepherded by Turkey and Brazil were "encouraging" but that Tehran must comply with Security Council resolutions.

On Friday, Ban's speech was full of praise for Turkey's diplomatic efforts.

Turkey has been a strong opponent of plans to impose further international sanctions on Iran, saying Iran has shown the political will to solve the seven-year-old nuclear standoff.

Turkish Prime Minister Tayyip Erdogan spoke by phone with Obama and Russian Prime Minister Vladimir Putin this week to stress the importance of Monday's deal.

On Friday, Erdogan's office published details of a letter he had sent Obama, underlining Turkey's commitment.

"The declaration has not closed the file on Iran's nuclear program but has opened an important door for a solution through diplomatic means," Erdogan wrote. "Turkey will continue its efforts for the solution of the problem and will pursue the issue."

Erdogan also spoke to Britain's new prime minister, David Cameron, who told him that "although the deal increases confidence, it does not solve the problem," Erdogan's official website said.

Ban was to hold talks with top Turkish officials in Istanbul and attend a reconstruction conference on Somalia on Saturday.