On board the presidential plane, Oct. 30 (CNA) President Tsai Ing-wen (蔡英文) has promised to boost Taiwan‘s defense budget by at least 2 percent each year, taking into consideration the United States‘ concern over a growing military imbalance between Taiwan and China, Tsai Ming-yen (蔡明彥), deputy secretary-general of the National Security Council (NSC), said Monday.