WASHINGTON (AFP) - The United States should set a May 15 deadline for Iraqis to form a unity government and then plan to withdraw its troops by year's end, Democratic Senator and former presidential candidate John Kerry said in commentary published in The New York Times. "If Iraqis aren't willing to build a unity government in the five months since the election, they're probably not willing to build one at all. The civil war will only get worse, and we will have no choice anyway but to leave," Kerry said. Joining a growing chorus criticizing the US-led occupation of Iraq,...