"We are seeing progress. The port and transit delays are improving," McMillon told President Joe Biden during a White House meeting with CEOs to discuss supply chain issues.
"Because of what you all did to help with overnight hours, and because of the team's work to reroute to other ports, to extend our lead times, and have other creative solutions, we have seen an increase in throughput over the last four weeks of about 26% nationally in terms of getting containers through ports," he said, joining the meeting virtually.
McMillon added that Walmart had noticed a 51% improvement in flow through Southern California ports, a big help for key holiday categories like toys.
Biden, who is wrestling with U.S. inflation that recently hit a 31-year high, has taken measures to try to break supply chain logjams, including unclogging ports and expanding trucker hours.
The Democratic president has also sought investigations into excessive shipping fees and possible illegal conduct into oil and gas markets that are keeping fuel prices high.
The meeting also featured participation from the CEOs of Best Buy Co Inc, Food Lion, Samsung North America, Qurate Retail Group, Todos Supermarket, Etsy Inc, Mattel Inc and Kroger Co, the White House said.
CVS Health Corp CEO Karen Lynch also participated virtually.
Biden was scheduled to make remarks about the supply chain, economy and efforts to combat inflation following the meeting, but the White House unexpectedly moved the speech to Wednesday less than an hour before it was slated to begin.
The president "wanted to ensure ample time spent with the business leaders who traveled to the White House today," a White House official said by way of explanation, noting that the press was able to attend the beginning of the summit.
Monday's meeting follows the start of the year-end shopping season. Black Friday retail sales were up 29.8% versus 2020 through 3 p.m. that day, according to Mastercard SpendingPulse.
Bargain hunters who ventured out to buy Christmas gifts on the day after the U.S. Thanksgiving holiday found stores less crowded amid a shift online, COVID fears and less-steep discounts.
U.S. retailers are estimated to generate online sales of up to $11.3 billion on Cyber Monday, a decline in growth from a year earlier as fewer discounts and limited choices due to global supply chain disruptions deter shoppers.
(Reporting by Alexandra Alper and Doina Chiacu,; Editing by Peter Graff, Ed Osmond and Marguerita Choy)