British Foreign Secretary Philip Hammond has said progress has been made between Iran and major powers over Tehran's nuclear program, despite passing Tuesday's midnight deadline, but said "key issues" still need to be resolved.
"I think we have a broad framework of understanding, but there are still some key issues that have to be worked through," Hammond told the BBC.
"Some of them are quite detailed and technical so there is still quite a lot of work to do but we are on it now and we'll keep going at it," he added.
The so-called P5+1 - the US, UK, France, China, Russia plus Germany - hope to limit Iran's nuclear ambitions in exchange for relief from sanctions which have left its economy crippled.