NEW YORK - A shift in the timing of the Easter holiday this year is likely to mean a nice gift's about to be delivered for retailers: Sales gains for March might turn out to be the industry's biggest in 16 years.

The International Council of Shopping Centers on Tuesday raised its March sales estimate to an increase of 8 percent to 10 percent, up from a previous outlook of a gain of 3 percent to 3.5 percent. The updated growth forecast could represent the sector's biggest increase since March 1994, said Michael Niemira, the ICSC's chief economist.

About six percentage points of the expected gain reflected the contribution from Easter falling this year on April 4, and thus being included as part of retailers' March reporting month, instead of April 12 last year.

Warmer weather, pent-up demand and easy comparisons against a downbeat consumer mindset a year earlier have also added fuel to retailers' momentum in March as consumer confidence improved and the U.S. economy created the largest jump in nonfarm payrolls recorded in three years. Research firm Retail Metrics said Wall Street's March sales estimates have continued to rise, most recently to an average gain of 6 percent on Tuesday from 5.5 percent on March 10.

Import cargo volume in March also suggested a strong month for retailers. It was estimated to have risen 6 percent, in what would be the fourth such monthly gain in a row, according to trade group National Retail Federation.

"Part of the pullback in spending during the recession was fear-based and as fear eased, spending picked up," said Thomas Weisel Partners analyst Liz Dunn.

Still, with retail stocks reaching their 52-week high and outpacing the broader market's performance, the key question is whether the purchase of spring dresses and gardening gear will continue in April and the months beyond, analysts said.

Most retailers are scheduled to report their sales numbers for last month on Thursday.

"Solid March results may be offset by a cautious tone on April," said J.P. Morgan analyst Charles Grom. "It is very difficult to gauge how much of (retailers') seasonal business was pulled forward into March from not only the earlier holiday, but also from ideal spring weather for a good portion of the month."

Combining retailers' March and April results would be a better gauge of whether consumer spending has fully recovered, analysts said.

For instance, in 1993 and 1994 when there was a similar calendar shift, March sales at the time had a 10-point jump, followed by a near flat reading in April, Niemira said.

March was the fifth warmest in 50 years in North America, according to weather consulting firm Planalytics.

With March being retailers' biggest month in the quarter by sales volume, chains may raise their profit estimates if sales turn out better than expected, analysts said.

Discounters, department stores and teen-apparel retailers are expected to post the biggest gains in March.

Led by Costco Wholesale Corp., the discount group is likely going to see an average 8.3 percent gain, according to Thomson Reuters.

The department-store segment's expected to see an 8.1 percent increase, led by double-digit gains forecast for Kohl's Corp. and Nordstrom Inc.

And in the teen sector, analysts estimated gains of 7 percent, paced by 10 percent or greater growth for American Eagle Outfitters Inc. as well as Aeropostale Inc., Thomson Reuters data showed.

In the apparel segment, Victoria's Secret parent Limited Brands Inc. will likely post an average increase of 6.6 percent, with off-price retailers TJX Cos. and Ross Stores Inc. estimated to post gains of about 6 percent each, and No. 1 U.S. clothing chain Gap Inc. likely to generate a 4 percent increase, Thomson Reuters survey of analysts showed.

While the actual number will very likely weaken in April, Wall Street said retailers have done a good job controlling their inventory and have shored up their offerings to entice consumers to spend, especially paying more at full price.

J.C. Penney Co., for instance, featured commercials during the Academy Awards in March touting an array of exclusive and private-label merchandise including I Heart Ronson by designer Charlotte Ronson.

For its part, Target Corp. launched designer Jean Paul Gaultier's limited collection, while Gap recycled old jeans and gave discounts for purchase of a new pair.

Victoria's Secret introduced its Body by Victoria's bras, including a new racerback style, through a I Love My Body by Victoria campaign.

"Retailers are definitely doing a better job with retail inventory and on-trend merchandise," Jharonne Martis, an analyst at Thomson Reuters, told MarketWatch. "We are seeing consumers spend freely again."