As a strike at U.S. East and Gulf Coast ports enters its third day, economic research firm Moody's Analytics warns that economic impacts will only escalate as the work stoppage drags on.

The firm estimates that the strike could lead to a $500 million daily hit to the U.S. economy within the next few days, with that number rising to as much as $2 billion a day if the situation persists for the next several weeks. The New York Post reported September 30 that an analysis by J.P. Morgan estimated a strike would cost the U.S. economy up to $5 billion per day.

The good news, though, is that retailers who would normally be relying on East and Gulf Coast ports during the peak holiday shipping season in October stocked up their inventories in the lead-up to the strike, when it became clear that negotiations between the International Longshoremen's Association (ILA) and the U.S. Maritime Alliance (USMX) had arrived at a standstill. 

Read More: Strike at U.S. Ports Brings Debate Over Automation Front and Center

"Negotiations were known to be fraught several months ahead of time, allowing businesses to prepare for this eventuality in a number of key ways," Moody's Analytics said in a report released on October 2, noting that many retailers also started rerouting shipments to West Coast ports in August.

That said, other industries are expected to bear the brunt of the work stoppage, including Asia-Pacific manufacturers for vehicles, semiconductors and furniture. Moody's Analytics estimates that roughly 20% of total Asian seaborne exports to the U.S. — primarily composed of the three aforementioned sectors — typically pass through the 14 largest East and Gulf Coast ports that are now closed. 

In the meantime, talks between the ILA and USMX on a new collective bargaining agreement have yet to resume. The ILA cut off negotiations in June after discovering that a handful of ports were using automated gate systems to check in vehicles, and has refused to return to the table until the USMX agrees to include stringent limits on automation and substantial pay increases in the union's new contract. On October 2, the USMX said that it "cannot agree to preconditions to return to bargaining," while the ILA has accused the USMX of "distorting facts and misleading the public" regarding the proposed contract.