Iranian President Hassan Rouhani says he is prepared to engage in "time-bound and results-oriented" talks on his country's nuclear programme, reports BBC.
He told the UN General Assembly's annual meeting in New York that sanctions against Iran were "violent".
He also welcomed Syria's acceptance of the Chemical Weapons Convention and condemned the use of such weapons.
Earlier, US President Barack Obama said he was encouraged by Mr Rouhani's "more moderate course".
He told the General Assembly that the diplomatic approach to settling the dispute over Iran's nuclear programme must be tested.
Mr Rouhani, who was elected earlier this year, has pledged a more open approach in international affairs.
Iran is under UN and Western sanctions over its controversial nuclear programme.
Tehran says it is enriching uranium for peaceful purposes but the US and its allies, including Israel, suspect Iran's leaders of trying to build a nuclear weapon.
President Rouhani said the "so-called Iranian threat" was imaginary.
"Iran poses absolutely no threat to the world or the region," he said.
A much-touted informal encounter between Mr Rouhani and Mr Obama failed to materialize.
On Thursday, Iran's Foreign Minister Mohammad Javad Zarif will discuss its nuclear programme with US Secretary of State John Kerry - a rare instance of a formal encounter between the counterparts.
The meeting will be attended by foreign ministers from the other four permanent UN Security Council members - the UK, China, France and Russia - and also Germany, which make up the so-called P5+1.