“could badly damage U.S. credibility”

Not sure the US has any left …

“an accord that they believe has prevented Iran from assembling an arsenal of”

That’s not true. 

Despite the deliberately-poor reporting of corporate media, the illusory crisis warmongers in the US and Israel had hoped to leverage into war with the oil-rich regional rival only reinforced that, unlike those peddling these WMD lies, Iran doesn’t have nukes, nor a program for their development, nor was it working on one, nor had it violated its obligations as a signatory to the Nuclear Non-Proliferation Treaty.

All the agreement did was leverage economic warfare into additional concessions, ones Iran had no obligation to accept, as they violated its NNPT rights.

Sad to see the corporate mass media once more playing along with a US government dissemimating WMD lies in order to enable war.