NEW YORK (CNNMoney.com) - With 10 days left until Christmas, some retail experts are saying that holiday sales could come in surprisingly weak this year unless consumers step on it, and soon.

After a quick start on Black Friday, the day after Thanksgiving that traditionally marks the start of the holiday shopping season, shoppers appeared to go into hibernation.

Britt Beemer, chief executive of consumer-trend tracking firm America's Research Group, said his research indicates that only about 25 percent of consumers had finished holiday shopping as of last weekend, down from 28 percent a year ago.

Beemer said the lag is surprising and at odds with an expected ramp-up in buying that typically sets in the two weeks before Christmas.

In a note earlier this week, Merrill Lynch analyst Mark Friedman said the biggest holiday sales volume days tend to occur in that final two-week stretch, or what he calls the "most critical shopping period of the season" that accounts for more than 40 percent of holiday sales.

That's a pretty sizable chunk if you consider that the National Retail Federation estimates total sales this year for the key November-December shopping period are expected to be nearly $440 billion.

"The biggest surprise to me has been this absence of urgency on the part of consumers," said Marshal Cohen, industry analyst with market research firm NPD Group. "I've been doing this for a long time. Other than in 2001, I haven't seen such a lackluster tone during the holidays.

"This doesn't feel like Christmas to me," he added. "Some consumers have told me that they haven't even started their holiday shopping yet, others say they've already run out of money. If I can find a parking space in the first or second row of a major mall this close to Christmas, something's wrong."

Another sign of the spending softness: Tuesday's government report on November retail sales, which showed that consumers bought less than expected last month.

Observers say part of what's happening is that consumers have become increasingly savvy at playing the game of chicken. In other words, let's see who blinks first: Consumers who go in and buy or retailers who cut prices.

Merrill's Friedman wrote that this is particularly true this year because an extra Saturday before Christmas gives consumers a better opportunity to wait for last-minute deals.

Cohen at NPD Group agreed, though he noted the risk that it could turn into an expensive gamble for consumers.

For one thing, retailers have been very disciplined with their inventory planning going into the holidays. Second, merchants have largely been posting decent monthly sales at stores open at least a year -- a key retail measure known as same-store sales.

"Retailers aren't very nervous just yet," Cohen said. "Obviously companies want to protect their profit margins and won't discount heavily if they don't absolutely have to."

But all that could change if the shopping pace doesn't accelerate this coming weekend.

Wal-Mart (Research), the world's largest retailer, already indicated that it was committed to being aggressive with prices all the way up to Christmas.

"This coming weekend has to be big," said Beemer, who expects about 56 to 58 percent of consumers will have wrapped up their gift-buying by this Saturday and Sunday. "If it's not, then I would say that retailers are in big trouble."

Gift cards may become the "wild card" for retailers in the final week, he added. "Because there is nothing compelling out there for people to buy, I'll think there will be a huge gift card explosion in the last 10 days. People will take the easy way out."

The growing popularity of gift cards poses both an advantage and somewhat of a challenge to merchants. On the positive side, analysts say gift cards have successfully extended the holiday season into January as recipients hit stores to redeem their cards.

At the same time, retailers can't book the gift card purchases as sales until the cards are actually redeemed.

The other "wild card" may be the weather, Beemer said. "The last couple of weeks it's become much colder around the country. That puts people in a mood to do their Christmas shopping and buy warm clothes."

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