OMAN/WASHINGTON, Feb. 6 -- Iran and the United States (US) began high-stakes negotiations in Oman on Friday to resolve long-standing disputes over Tehran's nuclear programme. However, differences over the agenda and additional issues threaten to derail diplomacy and escalate regional tensions.

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While both sides have expressed willingness to engage, Washington has pushed to expand talks to include Iran's ballistic missiles, regional military activities, and human rights concerns, according to US Secretary of State Marco Rubio. Tehran, however, insists that discussions remain limited to the nuclear issue, with Foreign Minister Abbas Araqchi and US Middle East envoy Steve Witk...