New Delhi, April 12 -- After nearly a full day of intense negotiations, talks between Iran and the United States have collapsed without agreement. US Vice President JD Vance left Islamabad on Sunday without a peace deal after 21 hours of the most significant direct negotiations between the United States and Iran in over a decade, saying Tehran had refused to make a long-term commitment to abandon its nuclear weapons ambitions.

At the heart of the impasse lies a fundamental disagreement over Iran's nuclear ambitions.

JD Vance declined to relitigate 21 hours of private negotiations on a public podium, but he was unsparing about the core reason the talks collapsed: Iran would not commit to permanently forswearing nuclear weapons.

"The sim...