Washington accuses Moscow of 'sustained and repeated' violations of nuclear treaty after withdrawing from agreement

Experts downplay effectiveness of charm offensive and say even if Trump might want to engage Iran the same way he has North Korea, Tehran is not interested

Head of atomic research institute calls IAEA inspectors 'roaches' that should be barred from the country; says Iran should not limit its research

Trump administration reportedly withheld information from Congress, raising concern it is tacitly approving move; fears raised Riyadh could be seeking nuclear weapons

In region, Bolton says Tehran has only one reason to boost uranium enrichment -- 'to reduce the breakout time to produce nuclear weapons'

Nuclear Nonproliferation Treaty members -- every nation but India, Pakistan, North Korea and Israel -- gather every five years to examine how pact is working

In telephone conversation that lasts more than an hour, the leaders discuss North Korea, Ukraine, US-Russia trade and 'very, very briefly' Mueller's report