BEIJING (AP) — China is vowing to retaliate if the U.S. proceeds with the sale of advanced weaponry to Taiwan worth more than a billion dollars. The statement from China's defense ministry gave no specifics but the development marks a further deterioration in ties between Beijing and Washington that have hit their lowest ebb in decades. The State Department on Wednesday announced it had greenlighted the sale of 135 precision land attack missiles, associated equipment and training to Taiwan to improve its defense capabilities. China regards Taiwan as its own territory to be annexed by force if necessary. Washington maintains only unofficial relations with Taipei but U.S. law requires it to ensure Taiwan can maintain a credible defense.