NEW YORK, United States — US shoppers who missed out on deals this past Black Friday are expected to flock to online sites Cyber Monday, testing the limits for some retailers that have been investing heavily on their e-commerce operations to stay relevant in a brutal space.

Retailers across the country are fighting to entice people to come to their web sites, offering new services such as deliveries with no minimum order limits and an assortment of deals.

Amazon and Target are pushing free shipping with no purchase minimum for the first time this holiday season.

Cyber Monday is expected to draw over 75 million shoppers, according to research firm Planalytics. The much-hyped marketing day is expected to be the largest US online shopping day in history, yielding $7.8 billion in sales or 17.6 percent growth over last year, according to Adobe Analytics, which tracks transactions at most of the top US online retailers.

But retailers will also face a deluge of online orders, which will task their e-commerce sites. If not backed with the right IT infrastructure the lure will lead to headaches — forcing outages and other technical glitches due to heavy traffic.

On Black Friday, websites of clothing retailers J.Crew and Lululemon Athletica and home improvement chain Lowe's suffered technical difficulties because of huge orders. Website outage tracker DownDetector.com also reported that Walmart's website had some problems.

Toys are expected to have the biggest discounts on Cyber Monday, Adobe Analytics said, as retailers fill the void left by the bankruptcy of top US toy retailer Toys 'R' Us.

Target was offering 30 percent off on select toys, while Kohl's discounted Lego sets between 30 percent and 40 percent.

Clothing retailers such as Gap and Nordstrom are offering the same discounts as on Black Friday, with deals such as Gap's 50 percent off across all products on its website and Nordstrom's up to 60 percent on merchandise.

Other deals include: $198 wool cashmere cardigan being offered at $107 at Ralph Lauren, sweaters at American Eagle Outfitters being offered at half price, Victoria's Secret selling all bras, excluding PINK, at a 50 percent discount and Urban Outfitters giving customers $50 off on online purchases of $150 or more.

Shares of Amazon.com were up as much as 2.5 percent in premarket trading, while Macy's, Gap and Target also rose. The stocks closed lower on Friday.

This past Black Friday, online sales jumped more than 23 percent, crossing $6 billion, while online sales surpassed $3.7 billion on Thanksgiving, according to Adobe Analytics.

The National Retail Federation forecast US holiday retail sales, including online, in November and December will increase between 4.3 percent and 4.8 percent over 2017, for a total of $717.45 billion to $720.89 billion. That compares with an average annual increase of 3.9 percent over the past five years.

By Siddharth Cavale: editor: Bernard Orr