NEW YORK - Santa's sleigh didn't make it in time for Christmas for some this year because of shipping problems at UPS and FedEx.

Delays were blamed on poor weather earlier this week as well as overloaded systems. The shopping period this year was shorter than usual, and more buying was done online.

Neither company said how many packages were delayed but noted it was a small share of overall holiday shipments. While the bulk of consumers' holiday spending remains at physical stores, shopping online is increasingly popular and outstripping spending growth in stores at the mall.

The problems appear to have affected many parts of the country. Many were left with little or no time to make alternative plans.

"We apologize that our customers did not receive their packages on Christmas," said Natalie Godwin, a spokeswoman for United Parcel Service Inc.

UPS did not make pickups or deliveries Wednesday. Extra workers were being brought in Wednesday night to the company's hub in Louisville, Ky., to sort packages for Thursday and Friday delivery.

Godwin said "UPS will honor its peak shipments commitments" to customers who used its air delivery service. Those shipping by ground have no guarantee past Dec. 11. Godwin said she didn't know if customers would receive refunds.

Some FedEx customers were able to pick up packages Christmas Day at their local FedEx Express centers.

"We're sorry that there could be delays and we're contacting affected customers who have shipments available for pickup," said Scott Fiedler, a spokesman for FedEx Corp.

Amazon.com was notifying some customers affected by the UPS delays that it would refund any shipping charges and was giving a $20 credit toward a future purchase.