As Americans become even more reliant on delivery, hundreds of thousands of UPS workers this week could authorize a strike that will bring the world's biggest package courier to a standstill.

UPS workers will vote this week on whether to authorize a strike if their union -- the International Brotherhood of Teamsters -- does not reach a new contract with UPS by August 1st.

The vote results will be announced next week on June 16, the union said.

A nationwide UPS strike would be the largest work stoppage in US history. The union represents more than half of UPS's total global employee base -- 340,000 UPS Teamsters -- which includes drivers and package sorters.

Voting will occur in person both at local union halls and at the gates of UPS facilities, according to the Teamsters.

"The time has come to use our strongest leverage and officially remind UPS that hundreds of thousands of Teamsters are ready to withhold our labor to ensure UPS acts accordingly," said Sean M. O'Brien, Teamsters General President. "The National Committee strongly urges all UPS Teamsters to vote YES to authorize a strike. This is how we win."

UPS and the Teamsters have been negotiating since April. The company said they had reached agreements on several important issues last month including "operating priorities, the use of technology and in-vehicle camera" as well as noting "advanced discussions on many other topics."

The two sides are scheduled to continue negotiations this week.

At the heart of the negotiations for the union is improved pay and benefits and better working conditions, including adding air conditioning in the panel trucks used for UPS deliveries, which the union says poses a health risk for drivers.

A strike at UPS would affect nearly every household in the country. An estimated 6% of the nation's gross domestic product is moved in UPS trucks every year. The explosive growth of online retail has made the company and its drivers more crucial than ever to the nation's struggling supply chain. Beyond the company's home deliveries, it also delivers many of the goods found in stores, factories, and offices.

"All Teamsters at UPS must be ready to show these corporate executives how serious we are about our new contract. We've been organizing, training, and rallying in the lots. Now it's time to vote," said Fred Zuckerman, the Teamsters General Secretary-Treasurer. "UPS is going to give us what we've earned. But we have to fight like hell for it. We must be prepared to hit the streets August 1 if UPS screws this up."

In April, UPS signaled it was committed to reaching an agreement before then.

"Taking care of our people and delivering for our customers is our top priority," UPS said in a statement.

CNN's Chris Isidore contributed to this report.