The five-month-old nuclear negotiations between Iran and world powers is entering a new, challenging stage.

A possible oil deal with Russia, and a diplomatic storm over Iran's choice for its ambassador to the United Nations, are all piling on pressure.

The US said such a contract between Russia and Iran could undermine talks and trigger new sanctions.

The US and its allies hope to convince Iran to scale back uranium enrichment activities and give UN inspectors greater oversight.

Iran says its programme is entirely peaceful.

Al Jazeera's Gerald Tan reports.

Source: Al Jazeera