Iran's nuclear tactics leaves Biden with tough choices

A flare-up in tensions between the UN nuclear monitor and Iran this week has left US President Joe Biden in an increasingly tight jam.

The US leader opened his presidency with a pledge to return to the 2015 international agreement that aimed to prevent Tehran from building nuclear weapons, after predecessor Donald Trump unilaterally withdrew from it.

Negotiations to restore that agreement have been at an impasse for three months over the very last details.