The American Defence Secretary presents his visit as a sign of improving military relations between Washington and Beijing. He says he's building on the momentum provided by last year's presidential summit between Bill Clinton and Jiang Zemin. Both countries are committed to increasing transparency between their military establishments -- a project which gained in urgency after their tense naval standoff in the Taiwan Strait in 1996. So Mr Cohen's visit will see the signing of agreements on exchanges of military personnel and on preventing clashes at sea; and the American Defence Secretary will tour an underground air defence centre -- something he describes as a breakthrough in openness by the Chinese military.