NEW YORK (CNN/Money) - U.S. chain store sales increased last week compared with the same period a year ago, helped by cooler weather and sales that coaxed shoppers into buying fall merchandise, an industry report said Tuesday.

But another report showed that, overall, September sales are down from last month as consumers become more choosy with their purchases.

Sales at stores open at least a year, a key gauge known as same-store sales, rose 3.7 percent for the week ending Oct. 5, compared with the same period a year ago, the Bank of Tokyo-Mitsubishi and UBS Warburg reported Tuesday. Weekly sales were up 0.8 percent compared with the previous week.

Separately, Instinet's Redbook Retail Sales Average slipped 0.7 percent during the five retail weeks of September, compared with the same period in August.

"Sales were modestly improved in the final week of September compared with the previous week," the report said.

The Redbook average is compiled from a sample of general merchandise retailers representing about 9,000 stores.

Both reports come as most of the nation's retailers prepare to report their September same-store sales Thursday. Analysts are generally expecting September sales to be higher than the past few months, but mainly because of easier comparisons with last September, when sales plummeted following the terrorist attacks on the United States.

The Bank of Tokyo, which bases its forecasts on surveys of 83 retail chains, estimates an anemic 1.5 percent year over year increase in September sales despite a shopping rally that occurred at the end of August, which seemed to indicate things were picking up.

BTM called the September forecast "incredibly weak under the circumstances."

Disheartening economic news, job jitters, concern about a U.S. invasion of Iraq, and shaken confidence in the markets continue to weigh on consumers. They have not stopped spending, snapping up cars, furniture and houses, but, saddled with record debt, they have turned more cautious, restricting many purchases to everyday necessities such as toilet paper and groceries, and buying fewer things like clothing.

Compounding the situation for retailers is the West Coast port lockout, ongoing since Sept. 27, leaving many merchants worried they may not be able to move millions of dollars worth of inventory off the docks and onto store shelves by the start of the critical holiday season next month.

The National Retail Federation's latest forecast for the 2002 holiday season, including November and December, is for a 4 percent year-over-year increase.