Obama motives are questionable, to say the least.
He goes on to sanction Venezuela's leaders over perpetrating human rights and crushing political opponents, while striving a removal of sanctions against Iran, a state that endorse terrorism almost openly, that is responsible for hundreds of thousands of dead syrian civilians (Actively assisting the Syrian government and is considered a main, perhaps sole reason that Assad is still in control), that is responsible for thousands, perhaps tens of thousands, of dead Yemeni civilians, a state which openly state their imperialistic aspirations regarding Iraq and other surrounding countries, a state who's leaders openly call for the destruction of the only real free democracy in the middle east, not to mention all the executions and human rights violations it imposes on its own people.
The thing is, Iran shouldn't get sanctioned just over its nuclear aspirations, it should be kept under sanctions because of all the other atrocities being made with their backing.
The call for an agreement is not to deny Iran of its nuclear capabilities, its that Obama could leave a legacy of achievements after he failed doing so by tragically misreading the map during and after the "Arab spring" and his inability to stabalize Ukraine. i don't think the delicate balance in a hell zone such is the middle east should be violently shaken just because Obama wants some trophies to put on his shelf.