The prime minister of Libya’s U.N.-supported government on Friday shrugged off threats by his rival, the commander of a self-styled army waging a months-long offensive to capture the country’s capital, Tripoli, that the “zero hour” of the battle has begun. Prime Minister Fayez Sarraj called on Libyans to rally around him in the defense of the nation. Sarraj’s call came a day after Gen. Khalifa Hifter of the self-styled Libyan National Army declared a final, “decisive battle” to take Tripoli from Sarraj’s U.N.-supported government.