single-company strike in u.s. history could be just a week away. u.p.s. and the teamsters back at the negotiating table today. the two sides haven t met since they walked away following a marathon session over the july 4th weekend. u.p.s. knows they need to pay our members. reporter: since then, the teamsters who represent 340,000 u.p.s. workers have taken to the streets for rallies and practice pickets. president sean o brien leading the charge. this will be our defining moment in the teamsters union. it will be the defining moment for labor. we have organized. we re strategized. now it s time to pulverize. reporter: both u.p.s. and the union say 95% of the contract is done, but the 5% left unfinished is the biggest piece of the pie. pay. stuff doesn t go anywhere unless we move it. we re the ones that are making all that money and we don t see it, any of it. reporter: part-time workers