Chinese ninth seed Li Na reached the US Open second round on Monday with a 6-2, 6-3 win over Britain\'s Heather Watson, but had to endure a marathon rain break before sealing victory. Li, who had lost in the first round on her last two visits, will face Australia\'s Casey Dellacqua for a place in the last 32. Former French Open champion Li, buoyed by her recent Cincinnati triumph, led 6-2, 5-3 when rain forced the players off Court 17 for over two and a half hours. But on their return, Li needed just three minutes to complete her assignment, taking victory when Watson, the 2009 US Open junior champion, netted a backhand.