U.S. special envoy to Sudan Andrew S. Natsios said yesterday that momentum is building for a political settlement to the Darfur crisis after rebel groups agreed on a common platform last week for talks with the Sudanese government. U.N. officials in New York, meanwhile, offered details on preparations for a major expansion of the peacekeeping mission in Darfur, a vast, featureless region that has been the site of a civil war between Khartoum and a number of rebel groups. Mr. Natsios, in a telephone conference with reporters, said that on a visit to Sudan last month, he sensed a war-weariness...