UPDATE 1-UPS to halt pickups for heavy items before vote on contract offer

(Adds context on UPS revenue, UPS union membership)

LOS ANGELES, Nov 1 (Reuters) - United Parcel Service Inc has warned customers it will stop picking up shipments of heavy items next Wednesday to avoid potential freight disruptions before union voting on a tentative contract ends on Nov. 11, the company said on Thursday.

"Because we do not have a guarantee against a work stoppage, we cannot afford to put our customers' volume at risk of being stranded in our system," UPS said in a statement.

The halt in pickups for large shipments of goods bound for stores and other destinations will not affect small-package deliveries during the upcoming holiday season, UPS said.

UPS wrapped up contract discussions with the Teamsters National Freight Industry Negotiating Committee on Oct. 25. The union has already authorized a strike if members vote "no" on the final contract offer from UPS.

On Oct. 5, UPS freight division workers rejected an earlier contract offer. An extension agreement is set to expire on Nov. 12.

A strike by the 12,000 Teamsters covered by the contract would be the first at UPS in more than two decades.

The Teamsters represent 250,000 UPS employees.

Freight is significantly smaller than the parcel delivery business at UPS, limiting the impact of a strike. The Atlanta-based company had third-quarter freight revenue of $867 million, compared with U.S. Ground revenue of almost $7.5 billion, according to a regulatory filing.

(Reporting by Lisa Baertlein in Los Angeles; Editing by Peter Cooney)