Ahead of a looming UPS nationwide strike, Teamsters union President Sean O'Brien said during a rally speech in Atlanta Saturday, "We've legalized, strategized, now it's time to pulverize."

Speaking with CNN's Isabel Rosales, O'Brien said 95% of the contract has been negotiated, and "now we're down to economics, and UPS knows they need to pay our members, especially the part-timers."

A UPS spokesperson has said part-timers receive the same benefits as full-time workers. However, they do make less than full-time employees who make, on average, $95,000 a year, as CNN previously reported. Part-timers start by earning $16.20 an hour and are eligible for a higher hourly rate after 30 days. On average, part-time workers make $20 an hour, according to the spokesperson.

When asked what happens if a deal is not reached by July 31, O'Brien said they would withhold their labor on August 1 at 12:01 a.m.

"UPS represents our members that deliver goods and services that deliver 7% of gross national product," O'Brien added. "So, the [UPS] supply chain solutions will take a huge hit."

According to O'Brien, a strike would be felt both domestically and internationally. He claims "because the pilots union that represents the pilots for UPS have committed to us that they will not turn a wheel if the teamsters go on strike."

Part-time package handler Elizabeth Laster told CNN Saturday she's willing to go without pay if the strike takes place. After working at UPS for seven years she said she feels like the company is making millions of dollars while she struggles to survive and provide for her three sons.

"The packages don't move unless we move them ... we're the ones that are making all that money and we don't see it. How is that fair?"

Laster said the company has "already gotten our blood, our sweat and our tears ... just give us what we've worked for."