NEW YORK, Oct 14 (Reuters) - Eager to capture any holiday-related spending as early as possible this year, Walmart Inc, ASOS, Best Buy and other major retailers are turning Black Friday into a multi-day promotion.

Black Friday, held the day after the Thanksgiving public holiday, has long been one of the biggest shopping days of the year in the United States. Retailers count on customers opening up their wallets to score door-buster deals on gifts.

However, the COVID-19 pandemic has forced retailers to drastically rethink how they do business as consumer spending habits prove unpredictable, and while Black Friday remains a major marketing event for retailers, its relevance had already been fading greatly in recent years due to early online promotions.

"Amazon's Prime Day (in October) marks the earliest start of the full assortment holiday shopping season in 50 years, as COVID permanently reshapes the holiday calendar," said Hilding Anderson, head of retail strategy at consulting firm Publicis Sapient. "Black Friday may not exist as a recognizable form this year."

That has forced many retailers to match and discount much earlier in the season to remain competitive. A slew of retailers including Walmart, Target, Best Buy, and Kohl's, have announced plans to roll out their winter holiday promotions in October too.

Consumers getting a head start on holiday purchases could give retailers a better shot at increasing sales and improving revenue after "an incredibly challenging year," Anderson added.

Walmart, the world's largest retailer, said on Wednesday it would offer Walmart shoppers reduced prices on everything from TVs to bath towels and blenders during three separate promotions across a handful of days in November, which will help reduce crowds. The promos will begin online at Walmart.com and continue in Walmart stores, the company said.

On Tuesday, Best Buy sent an email to shoppers advertising deeply discounted laptops, tablets, printers and other items for their two-day "Black Friday Prices Guaranteed Sale" coinciding with Amazon's Prime Day.

A Best Buy spokesperson said on Wednesday it would give shoppers more opportunities to bag deep discounts on electronics in the run-up to the holiday in November.

ASOS Chief Executive Nick Beighton told Reuters on Wednesday the British online clothing retailer would also stretch its Black Friday promotions across several weeks. (Reporting by Melissa Fares in New York; Additional reporting by James Davey in London and Uday Sampath Kumar in Bengaluru; Editing by Sam Holmes and Cynthia Osterman)