What's going on with the Iran nuclear talks?

London — Iranian and U.S. negotiators resumed talks in Vienna on Thursday that could eventually resurrect the nuclear deal struck back in 2015. But that's a big could.

President Joe Biden's administration wants to reverse his predecessor's unilateral withdrawal from the agreement, but the process was always going to be delicate. Sunday's attack on Iran's nuclear facility in Natanz has complicated things even further. Iran responded to what it called an act of "nuclear terrorism" carried out by Israel by announcing that it would start enriching uranium to 60% purity — a big step up from its current maximum of 20%.