Iran Leader Endorses Nuclear Deal despite 'Ambiguities'

Iran's supreme leader Ayatollah Ali Khamenei explicitly endorsed a nuclear deal with world powers for the first time Wednesday, but warned his president it contained weaknesses that must be guarded against.

Despite more than two years of negotiations that culminated in a July 14 accord between Iran and world powers, Khamenei had never before said openly that he backed the diplomacy. Nor had he said he was against it.

The agreement with the five permanent members of the U.N. Security Council plus Germany will see a raft of trade sanctions against Iran lifted in return for curbs lasting up to 15 years on its atomic activities.

Khamenei permitted the nuclear talks that led to the agreement but the diplomacy gained momentum after the election of President Hassan Rouhani, a relative moderate, in June 2013.

The supreme leader's remarks on the nuclear deal came in a letter to Rouhani a week after a motion in Iran's parliament approved it, following months of often fierce opposition from hardliners about its terms.

Khamenei, who has the last word on all policy matters, said he had approved the decision of the country's top security committee, the Supreme National Security Council, to implement the deal.

However he told Rouhani that the agreement had "many ambiguities and structural weaknesses" which must be closely monitored and he repeated his long-held stance that the United States cannot be trusted.

"In the absence of tight control these could bring significant damage for the present and the future of the country," Khamenei said of what he called the deal's "ambiguities."

A committee, controlled by the SNSC, will be formed to monitor "possible breaches and deception by the other parties, in particular the U.S." he said in the letter, which was published on his website.

Iran has always denied pursuing an atomic weapon but Western intelligence agencies alleged that work to develop a bomb had taken place.

The lifting of sanctions is conditional on Iran putting stringent curbs on its nuclear program, including on its enrichment of uranium, the processing of which at high purities can produce bomb material.

The main provisions of the agreement, known officially as the Joint Comprehensive Plan of Action (JCPOA), extend for between eight to 15 years.

- IAEA probe due December 15 -

Khamenei said any new sanctions against Iran by the six other nations in the deal -- Britain, China, France, Russia and the United States plus Germany -- would be a fatal breach of the accord.

If such occurred "under any pretext by any country engaged in negotiations, it will be a violation of the JCPOA and the government will be obligated to stop the agreement," the 76-year-old leader said.

On Sunday, U.S. President Barack Obama and the European Union announced measures to ensure the lifting of sanctions, including those on Iran's banks and energy sector, as soon as international monitors have closed a probe into possible military dimensions of Tehran's past nuclear activities.

The U.N. nuclear watchdog, the International Atomic Energy Agency (IAEA) is due to complete its final report into potential military aspects of Iran's nuclear program by December 15.

The crucial "implementation day" of the deal can only happen after that.

Khamenei said the IAEA probe must be closed before Iranian officials will take steps to ensure its Arak reactor cannot produce plutonium -- another potential route to an atomic weapon.

China has agreed to work with Iran and the United States to re-engineer the Arak reactor so that it cannot produce plutonium, officials have said.

Another condition of the deal -- that Iran's stockpile of low-enriched uranium be exported out of the country -- also cannot be taken until the IAEA has completed its investigation, Khamenei stipulated.

Iran will also have to disable more than two-thirds of its 19,000 centrifuges -- fast-spinning machines that enrich uranium -- with just over 6,000 being left in place.

The nuclear agreement, which has brought Iran out of the diplomatic cold after years of high tension on the nuclear issue, has raised expectations of further detente.

However, since the deal was struck Khamenei has banned other negotiations with the United States, Iran's main adversary since the Islamic revolution toppled the U.S.-backed shah in 1979.