Iran's foreign minister headed to New York Tuesday to resume nuclear talks with major powers but it was unclear if there would be a repeat visit by President Hassan Rouhani, who launched Tehran's opening a year ago.

Foreign Minister Mohammad Javad Zarif was to hold a working lunch with European Union foreign policy chief Catherine Ashton, the lead negotiator for the six powers, his deputy Abbas Araqchi said.

The head of the U.N. atomic watchdog hit out Monday at Iran over its lack of cooperation with a probe into its nuclear program, three weeks after Tehran missed a deadline to provide important information.

"In order to resolve all outstanding issues, it is very important that Iran continues to implement, in a timely manner, all practical measures agreed" to improve transparency, International Atomic Energy Agency chief Yukiya Amano said.

Iran said Monday it rejected a U.S. request for its cooperation against the jihadist Islamic State as part of an international coalition whose true aim Tehran sees as regime change in Syria.

Seen from Tehran, which has helped both Damascus and Baghdad to confront IS advances, the coalition lacks credibility because some of its members had financed and armed the group as part of their campaign to bring down Syrian President Bashar Assad.

Tehran ridiculed an international conference on the jihadist threat that opened in Paris on Monday, insisting the Islamic State cannot be defeated without the support of its ally Damascus.

Neither Iran nor Syria were invited to the meeting in the French capital, despite the Damascus government's involvement in almost daily military action against IS.

Iran said Saturday it has no wish to attend an international conference in Paris next week on fighting the jihadist Islamic State group, dismissing the meeting as just for show.

"We have no interest in taking part in this counter-terrorism conference in Paris which has a selective guest list and is just for show," deputy foreign minister Hossein Amir-Abdollahian told state television.

A top Iranian nuclear negotiator said Saturday that "disagreements over serious questions" persisted in the latest talks with the world powers on his country's atomic program.

"After two rounds of negotiations with the European representatives, our positions have not been reconciled and disagreements over serious questions still exist," said Majid Takht-Ravanchi, who is also a deputy foreign minister.

An Iranian soldier was killed and two pro-government militiamen were wounded in a rebel attack on a border post with Pakistan in southeast Iran, state news agency IRNA reported Wednesday.

Commander Ramezan Sharif of the Revolutionary Guards, quoted by IRNA, said a soldier of the elite force was killed and two bassiji Islamist militia volunteers were wounded.

In finally tackling the jihadist threat in Syria and Iraq, Washington and Gulf Arab states are confronting a "monster" that has come back to bite them, partly through their own failings, analysts say.

After a stop Wednesday in Baghdad, U.S. Secretary of State John Kerry will hold talks Thursday with Arab states and Turkey in Saudi Arabia to broaden an international alliance set to act against the Islamic State movement (IS).

Iran accused the United States Sunday of not taking the threat from Islamic State militants in Iraq and Syria seriously, and charged that U.S. aid had previously helped the jihadists.

The United States and Iran have denied plans for any military coordination in the fight against Islamic State militants operating in Iraq and Syria.

"We are not going to coordinate military action or share intelligence with Iran and have no plans to do so," State Department deputy spokeswoman Marie Harf said Friday, reacting to reports that Tehran had approved such an arrangement.