Iranian diplomats voiced concerns in a meeting Monday with U.S. Secretary of State John Kerry about a letter sent by Republican U.S. lawmakers to Tehran’s leadership this month in which they threatened to block any agreement reached on Iran’s nuclear program, according to U.S. and Iranian officials. The letter wasn’t “helpful” to the negotiations, said a senior U.S. official, and was raised in talks by Iranian Foreign Minister Javad Zarif with Mr. Kerry during roughly five hours of meetings at the Swiss lakeside city of Lausanne on Monday. But the American diplomat stressed the U.S. and Iranian sides remained committed to forging a comprehensive agreement to curtail Iran’s nuclear program by a March 31 diplomatic deadline. The official added that […]