U.S. Secretary of State John Kerry started a record ninth-straight day of nuclear talks on Sunday in Vienna, a day after United Nations monitors announced a breakthrough that should ease concerns over Iran�s past.

Kerry began morning meetings at the Palais Coburg with Iranian Foreign Minister Mohammad Javad Zarif, a U.S. administration official said. Foreign ministers from the other five nations attending talks -- China, France, Germany, Russia and the U.K. -- will begin returning this afternoon in an attempt to finalize an agreement by Tuesday.

�The extension of negotiations is not a desired alternative for any of the parties,� Zarif�s deputy, Abbas Araghchi, said Saturday on state television. �All parties involved are determined to come to a conclusive end.�

This is the 20th round of high-level talks since U.S. President Barack Obama and Iranian President Hassan Rouhani opened negotiations nearly two years ago. After Kerry negotiated for eight straight days at the previous round in Lausanne, Switzerland, diplomatic historians called it the longest continuous senior-level meeting since the 1978 Camp David accords.

Much of the past week has involved discussions with International Atomic Energy Agency director general Yukiya Amano. While the IAEA isn�t formally a party to the negotiations, it will play a key role in implementing a final accord.

Amano said Saturday that his inspectors, now in the 12th year of an investigation into possible military dimensions of Iran�s nuclear past, said his agency can provide its assessment by December.

Key Demand
�With the cooperation of Iran, I believe we can issue a report by the end of the year,� Amano told reporters.

Resolving issues of past concern is a key demand Iran must meet to win sanctions relief. One diplomat said Iran may be able to win �substantial� sanctions relief by December while others said it may take until the first quarter of 2016.

Israeli Prime Minister Benjamin Netanyahu, a staunch critic of the deal emerging in Vienna, called the talks a �breakdown� and not a breakthrough.

The officials in Vienna, who asked not to be identified in line with diplomatic rules, said much of last week was given to rebuilding trust between the IAEA and Iran. Agency inspectors have rebuked Iran for insufficient cooperation while the Islamic Republic complained it was unfairly singled out.

Sides have concentrated on finalizing two lists of sites about which inspectors need more information. One list focuses on the steps needed to clear concern over Iran�s past. A second list comprises Iran�s declared nuclear- and nuclear-related sites, which will need to be updated every three months after the IAEA implements more stringent monitoring.
Suspicious Activity
Iran wants to avoid a spike in so-called �Complementary Access� requests once it adopts that IAEA�s so-called �Additional Protocol,� one of the diplomats said. Those visits are called by agency monitors when they receive reliable and actionable information about possible nuclear-related activities at a non-declared site.

In 2014, there were 78 total complementary access requests among all 125 countries implementing the Additional Protocol. Japan, at 19, had the most IAEA requests for special visits. Most countries didn�t receive any requests.

To avoid the appearance that it�s being unfairly singled out after it adopts the Additional Protocol, Iran will need to boost cooperation and allow more site access by December, the diplomats said.

By Bloomberg