"On the whole I am optimistic ... but there are those who have an interest in more troubles and not dealing with this question have not been inactive. They are trying to make sure there is no deal," Salehi said on the sidelines of talks in Lausanne of Switzerland.

Iranian and US diplomacy chiefs have begins new round of talks in Lausanne as part of broader negotiations between Iran and six world powers aimed at reaching a final deal over iran’s nuclear program.

Thursday’s talks between Iranian Foreign Minister Mohammad Javad Zarif and US Secretary of State John Kerry come hot on the heels of deputy-level negotiations a day earlier which brought together Iranian deputy foreign ministers Abbas Araqchi and Majid Takht-e Ravanchi, US Under Secretary of State for Political Affairs Wendy Sherman and EU deputy foreign policy chief Helga Schmid in Lausanne.

Also present in Thursday’s negotiations are US Energy Secretary Ernest Moniz and head of the Atomic Energy Organization of Iran Ali Akbar Salehi as well as the four officials who sat down for talks Wednesday - Araqchi, Takht-e Ravanchi, Sherman and Schmid.