TAIPEI - Taiwan's defense ministry said on Wednesday that an upgrade package for its ageing F-16 fighter jets offered by the United States will contribute to regional peace by improving Taiwan's defense capability in the face of a continued threat from mainland China.The Obama administration formally notified the US Congress on Wednesday of a potential $5.3 billion upgrade of Taiwan's existing fleet of US-built F-16 fighter jets, a move that China is certain to oppose."Mainland China's military expansion and threat against Taiwan still exist," Taiwan's defense ministry said in a statement."Improving our defense capability is a crucial and only measure to sustain regional security and stable development across the (Taiwan) strait."