DUSHANBE, July 23 (Reuters) - Tajikistan is preparing to take in up to 100,000 refugees from neighbouring Afghanistan where fighting has escalated as United States-led troops withdraw, a senior Tajik official said on Friday. Taliban insurgents are gaining control of more and more territory in Afghanistan, which the Pentagon estimates now extends to over half of Afghanistan"s district centres. Imomali Ibrohimzoda, deputy head of Tajikistan"s emergencies committee, told a briefing on Friday the former Soviet republic was already building two large warehouses to store supplies for refugees in the Khatlon and Gorno-Badakhshan provinces adjacent to the border. A few hundred Afghan civilians fled to Tajikistan this month but the Dushanbe government says they have already returned to Afghanistan.