Already mired in a sales slump, Gap Inc. has closed its two most popular Internet stores so the clothing retailer can upgrade its online operations before the pivotal Christmas shopping season. Both Gap.com and Oldnavy.com have been closed for the past week, driving frustrated shoppers to other web sites to buy clothes. Banana Republic, another chain owned by Gap, also closed its site two days last week before reopening Aug. 26.

Hoping to minimize the customer inconvenience, Gap Inc. waited until after most back-to-school shopping had been finished before launching a "soup-to-nuts" overhaul of its major e-commerce sites, said company spokeswoman Kris Marubio. "We think this is going to make for a more compelling and exciting experience for shoppers," Marubio said. The San Francisco-based company isn't disclosing when the sites will reopen. Instead, visitors are being asked to leave their e-mail addresses with Gap.com and Oldnavy.com so they can be informed when the sites are selling clothes again.

"It's major project for us so we know it's going to take some time," Marubio said. She warned the company may still have to fix some bugs even after the sites reopen. The continuing closure of Gap.com and Oldnavy.com is likely to put another small dent in Gap Inc.'s sales, which have been sagging in recent months. The slump already has prompted management to lower its profit projections for this year. Gap.com and OldNavy.com each generated online sales of $236 million last year, accounting for 3% of Gap Inc.'s total revenue of $16.3 billion. Oldnavy.com attracted 4.2 million visitors in July while Gap.com drew 2.6 million visitors, according to Nielsen/NetRatings, a research firm.