US Secretary of State John Kerry on Wednesday voiced regret over the handling of the arrest of an Indian diplomat, in a phone call to a top Indian official amid an escalating row between the two countries. The top US diplomat called National Security Advisor Shivshankar Menon and said he "empathizes with the sensitivities we are hearing from India about the events... and in his conversation with National Security Advisor Menon he expressed his regret," a State Department spokeswoman said.