[Rusty Backhand]

NEW YORK, Sept 6 (Reuters) - Roger Federer's U.S. Open title defence came under threat for the first time on Tuesday when he was tested by German Nicolas Kiefer before reaching the quarter-finals at Flushing Meadows.

http://go.reuters.co.uk/newsArticle.jhtml?type=tennisNews&storyID=9578276&section=news&src=rss/uk/tennisNews