Some large retailers and other companies across the country are warning customers of potential delivery delays if there is a UPS strike.

The International Brotherhood of Teamsters union, which represents 340,000 members at Sandy Springs-based UPS, has threatened to strike Aug. 1 if there is not a deal for a new labor agreement struck by that time.

The two sides are set to resume talks on Tuesday, leaving a week for them to reach a deal before the deadline.

The Teamsters contract at UPS, which is set to expire July 31, is the largest private collective agreement in North America. If there is a strike, it would be the nation’s largest since 1959 when the United Steelworkers of America went on strike.

Toothpaste maker Crest on its website says UPS is its primary shipping partner, and it will cancel all orders placed for delivery to P.O. box addresses from July 21 to July 25. It has also put Crest subscriptions on hold. Other orders placed July 21-25 will be upgraded to 2-day shipping.

If there is a UPS strike, Crest tells its customers: “This will lead to significant shipping delays and backlogs are to be expected.”

Crest also said if there isn’t a resolution between UPS and the Teamsters, it will “likely have to pause new orders for products sold exclusively on Crest.com starting July 26th.” However, it said most Crest products will still be available in person at retailers.

UPS is losing some business as its customers’ concerns grow about the impact of a potential strike.

Crest’s UPS Strike FAQs includes: “Is Crest looking at other options to accommodate orders in the future?” Its answer: “Crest is exploring other shipping options and will update information as it becomes available.”

UPS said Monday that “we look forward to getting back to the negotiating table tomorrow and are focused on reaching agreements that provide wins for our employees, the union, UPS and our customers.”

Qiagen, a biotech firm that makes DNA and RNA extraction kits, blood tests and other products that it ships to labs and hospitals via UPS, is also warning its customers about the impact of a potential UPS strike.

Qiagen on its website advises its customers to place orders for essential items by Wednesday, July 26, for delivery before the end of July, to “help avoid any potential shipping delays.” The company also said it is looking at “alternative shipping options through carriers other than UPS.”

“We understand the uncertainty surrounding this situation, which is beyond all of our control. But please be assured we are doing everything possible to find ways to maintain our high level of service and keep disruptions to the lowest possible level,” Qiagen says on its website.

Pearson Assessments, which sells tests and assessments for academics and professional use, acknowledged to its customers that “we know you depend on receiving important materials on time for your clinical practice and the back-to-school season,” according to a notice posted on its website.

Pearson Assessments told its customers that it would pause shipping with UPS on July 25 in anticipation of the strike and has “arranged for other carriers to handle shipments.”

“Because other UPS customers will likely do the same, however, delays are still possible,” Pearson Assessments said. “If you have time-sensitive orders, we recommend placing those as soon as possible to have the best chance of receiving them in a timely manner.”

Comcast Internet and TV service Xfinity on its website tells customers that it anticipates there will be delays in orders of its equipment and devices if there is a strike.

“If you can’t return your equipment to an Xfinity Retail Store, you can hold on to it until the strike is over, at which point you can return it to a UPS store or schedule a UPS at-home pickup. However, you may see unreturned equipment fees on your account,” Xfinity says on its website. The company says those fees will be removed once the equipment is returned.

It advised that “due to the uncertainty of UPS Store operations, we recommend returning your equipment to an Xfinity Retail Store whenever possible.”

Are your shipments affected by a potential UPS strike? Email kyamanouchi@ajc.com to let us know.