Foreign Secretary William Hague has warned Iran it faces increasing isolation from the international community after talks on the future of its nuclear programme ended without a deal.
Six world powers failed to secure an agreement from Iran that it would cut back on its highest grade uranium enrichment production in return for a relaxation of sanctions.
Mr Hague said a "wide gap remains" between Tehran and the so-called E3+3 nations - the UK, United States, France, Germany, Russia and China - despite two days of negotiations in Kazakhstan.
"The UK went to Kazakhstan ready with our partners to negotiate in good faith with Iran," he said.
"Lengthy discussions took place on some issues, but a wide gap remains between the parties. Iran's current position falls far short of what is needed to achieve a diplomatic breakthrough.
"We look to Iran to consider carefully whether it wants to continue on its current course, and face increasing pressure and isolation from the international community, or to enter into meaningful negotiations."