The 2017 US holiday shopping season remains on track to produce solid growth after more than half the US population made purchases over the Thanksgiving weekend, the National Retail Federation said Tuesday.

NRF officials cited strong US economic data, good weather and an enterprising approach by retailers to discounting both in store and online as factors boosting their continued confidence in the outlook.

The organization estimates total holiday sales will rise between 3.6 and 4.0 percent compared with last year.

"From good weather across the country to low unemployment and strong consumer confidence, the climate was right, literally and figuratively, for consumers to tackle their holiday shopping lists online and in stores," NRF chief executive Matthew Shay said in a news release.

The US holiday shopping season officially opened last week with sales on "Black Friday," the day after Thanksgiving, and picked up momentum into "Cyber Monday."

During that five-day stretch, more than 174 million people made purchases, with over 58 million buying online only, and more than 51 million spending in brick-and-mortar stores, while over 64 million spread their spending among both.

The average spending per person over the five-day period was $335.47, according to the survey.

The NRF's upbeat appraisal came on the same day the Conference Board reported that consumer confidence stood at a 17-year high. The shopping outlook is consistent with other forecasts projecting an improvement on the last couple of years.

Still, retailers are aware the winter shopping season is protracted and a good start doesn't always mean much, since outside factors could influence consumer spending decisions. 

President Donald Trump raised the possibility of a government shutdown Tuesday in a Twitter statement that prompted Democratic leaders in Congress to cancel talks on a budget extension. North Korea also moved back into focus, after the country fired a ballistic missile, according to South Korean military officials.

Shay did not directly address either issue during a briefing with reporters, but cautioned that there are "4-1/2 weeks to go, so lots of things can change."

Even so, "we're actively encouraged that we have a strong start."

Also unknown at this point is the extent that heavy discounting will cut into retailer profits, even if overall sales are good. That can sometimes lead to disappointing results when retailers report earnings in February.

Shay said promotions are as aggressive as last year and buying items on sale remains a priority for many shoppers