Heavy rain delayed the start of day nine at the US Open on Tuesday, leaving defending champion Rafael Nadal and title rival Andy Murray kicking their heels in frustration. The downpours again looked set to spark more questions over the decision by the Flushing Meadows authorities not to follow the lead of the Australian Open and Wimbledon in building a retractable roof over its main court. Rain has bedevilled the tournament in recent times with the men's final, scheduled for the last Sunday of the fortnight, carried over to the Monday for the last three years. "The current forecast calls for showers to continue for the next few hours followed by a period of dryness, when we hope to begin match play," said a statement released by organisers just before the scheduled 1100 (1500GMT) start. Murray was due to begin proceedings on the Arthur Ashe Stadium against Donald Young of the United States followed by Nadal's clash against Gilles Muller of Luxembourg. In the day's other men's last 16 matches, Spain's David Ferrer was to face former champion Andy Roddick with John Isner tackling Gilles Simon. The first two women's quarter-finals were also due to begin with Angelique Kerber of Germany playing Italy's Flavia Pennetta and Samantha Stosur of Australia taking on Russia's Vera Zvonareva.