Iran and a group of six nations led by the United States have agreed to a historic accord to significantly limit Tehran’s nuclear ability for more than a decade in return for lifting international oil and financial sanctions against Iran, a senior Western diplomat involved in the negotiations said on Tuesday. The deal, which President Obama had long sought as the biggest diplomatic achievement of his presidency, culminates 20 months of negotiations. A formal announcement of the agreement was expected later on Tuesday, when foreign ministers from Iran and the six nations it has been negotiating with will meet at a United Nations complex in Vienna. Catherine Ray, a spokeswoman for the European Union, said a final plenary meeting […]