The negotiations have been framed by Trump as both countries’ best chance to avoid direct military conflict over Iran’s nuclear program. Tehran, which denies seeking a nuclear weapon, has insisted that it will not agree to any deal that fully scraps its enrichment program.

Iran Supreme Leader Ayatollah Ali Khamenei Wednesday dismissed a U.S. proposal to halt Iranian uranium enrichment, appearing to reject a central U.S. demand in the nuclear program talks.

After five round of talks, several hard-to-bridge issues remain, including Iran's insistence on maintaining uranium enrichment on its soil and Tehran's refusal to ship abroad its