Nikkei slips on weak economic data, posts big monthly gain

TOKYO, Sept 30 (Reuters) - Japanese stocks fell to a one-week low on Tuesday as a one-two punch of weak economic data and a profit warning from Sumitomo Corp knocked out sentiment - but for the month the Nikkei posted its biggest gain since last November. The Nikkei share average fell 0.8 percent to 16,173.52, the lowest closing level since Sept. 24. For the month, the benchmark rose 4.9 percent helped by the weakening yen and building momentum in the U.S. economy. It was the biggest mon