A meeting on Libya in London next week will seek to break a political stalemate over the country's U.N-backed unity government, which has struggled to extend its influence beyond the capital, Tripoli, a senior U.S. official said on Friday. Monday's ministerial meeting, convened by Britain and the United States, takes place as Libyan forces close in on the key city of Sirte, hoping to flush out Islamic State forces that grabbed it during factional infighting more than a year ago after the fall of strongman Muammar Gaddafi in 2011. ......